I added edits how to handle situation in fairly hostile planet (no immediately edible animals or plants), and with fairly limited crew size.
ALL colonists would be young women PhD biologists (with few mechanics/electronics engineers added) in their twenties and early thirties. Smartest ones, very healthy, genetically screened. Few genius teenagers, to stagger fertility (after age 40 fertility diminishes and chance of genetic diseases increases dramatically). And many (tens of thousands) samples of frozen sperm for later, to maintain genetic variability. Would not make sense to waste such limited space on men, if you can grow them up later - when you are sure you can feed them.
Not sure why and how is your limit on number of colonists: Is it total weight of the cargo in spaceship? Because if weight is the limit, it could make sense bring less crew but more cargo which would help to establish colony faster (because cargo does not need food and life support during the flight). And spaceship can provide life support after landing too, for exactly same number of crew.
If planet has breathable air, it has some life (which created oxygen), and likely some kind of plant and animals - at least algae and fungi. So you can assume you can harvest such resources for needs of your colony, and consume them after some transformation. From original post, it is hard to guess how different the biology of host planet is, and how much transformation will be necessary.
Depending on natural resources, you can support such small population by hunting/fishing (which require easy to gain skills) for first decade (kids don't eat much - spaceship can provide for same population), while working on developing basic industrial technologies. You need also a way to explore planet fast, to land in a place with lots of natural resources. Your aim would be resources for steam age technologies. Coal and iron, next to reasonably fertile plains.
You would need to observe weather and seasons, and be ready to relocate few times - which should not be too hard, because for first at least decade you would live in spaceship anyway.
Taming animals also can be established quickly: experimental domestication of silver fox done in 50 years (20 generations). You need easy source of food, like insects or fish.
You will include also huge library, so young crew-members can learn from experience of others on Earth, and not from own mistakes.
Depending on how much time you have, you may even try to run simulations of such settlement on Earth, with colonist trained in developing steam-age technology from scratch: outside world provides them raw materials, but they need to figure out how to build needed tools, and manage community and not to kill each other. And they have whole tool-building factory on spaceship (and lots of metal). So elder colonist would be best veterans of such training, who did such boot-up few times, and youngest at least once. So they could be preparing for such mission for a decade or more. If you have few decades, you can set up whole culture about that: mothers training their daughters to be experts in necessary technologies, preparing lab technologies which are automated and easy to repair, etc.
Think about Ender's Game Room, but for female double major PhD biologists and mechanical engineers. If you are selecting only one of hundred million, you can be very picky - and people will be motivated to learn necessary skills.
Farming and hunting is a basic skill which any person preparing for such mission can pick relatively quickly. Plant biologist will naturally cross-train as farmer, and animal biologist or geologist as hunter. You need also "tool people" like mechanical engineer, builder, miners, chemist. And medical personnel, especially gynecologists and psychologist, including children psychology. All women of course.
If you have really long time to prepare, many can be children who were born and raised in such simulation camps on Earth. Raised from sperm of men who have very gifted daughters, by teachers trained for such situation (no male examples).
There is a danger that women on such colony would like life without men, and would not raise any until there are many thousands of women - planet of Amazons indeed. :-)
In worst case scenario, none of local lifeforms are usable for humans, and you need to develop ecology. You will need more biologists (or more time). They will have to design bacteria which can digest local lifeforms and grow and be fed to higher life forms usable by humans, like: algae, fungi, then insects, chicken. It will be long slog, might take several generations of (all female) researchers to develop necessary technologies.
During this time, colony would be supported by original life support system from spaceship (powered by solar energy), and would not be able to grow numbers beyond what life support system can feed.
So if you are very unlucky, and very limited, you have crew of say 100 female biologists (few cross-trained in medicine) supported for several generations ONLY by life support from spaceship, trying to figure out how to use local life-forms to sustain humans. No men needed, focus 100% on research and training next generation. Women get artificially inseminated to born new generation of girls (one replacement girl each) to train them and continue development of ecology until they figure out what grows and can sustain the colony. Likely girls will have to prove themselves to be smart and team players very fast (IQ test by age 6), or be disposed of (used for human experiments) to be replaced with more promising sibling. It will be very brutal, but such planet will not be a place for weak - or even for average. Until we can feed everyone, we can afford to feed only the extraordinary - or die out.
Only after basic farming is established they can consider increasing size of the colony beyond what spaceship life support can provide for, and spend resources on developing additional technologies (after learning them from ship's library), mining resources, building outside structures, growing the colony.
Even then, you would want to try local food only on few volunteers (human experiments again) to see longer-term consequences before you commit whole colony to new food. You have no margin or error to i.e. local food in some way causing birth defects after 20 years of consuming it. So likely young population (before and during fertility) will stay on original Earth food for even longer, after older (past 40) will try to "go native" - and possibly suffer the consequences.
Genetic diversity is not a problem at all, you may have several thousand samples of sperm, to start using in different generations. If you have time, you can even select fathers by ability and skill: science skills, engineering/manufacturing skills, fierce fighter skills, as expressed in their daughters. With frozen sperm, problem is not genetic diversity but sustaining life in the colony.
If you can have some experts in hibernation, that could help: you will thaw them when you need expertize, and refreeze then in between. Will be extremely harsh world, with very strict morale about living only to contribute to survival of the colony. No slackers.
You need defense to protect your colony. Best weapons would be something where you need to add just energy (from solar) and not chemicals (which you need to bring with you [expensive cargo] or mine and manufacture locally [distracting you from survival]. Mechanical catapults using local rocks fits the bill.
You know it already, but with such stacked deck, you have VERY small margin of error, and any small mistake might wipe out your colony. Sending multiple spaceships will make much sense. it will also limit consequences of choosing wrong landing place - because even if relocation will be possible, will not be simple nor easy nor cheap.
Absolute minimal limit might be as little as maybe dozen female biologists/engineers, with spaceship capable to support them for many decades until they will develop ecological way to support bigger population from local resources. Really tough. Could be good story.