I'm relying heavily on the posted image, because the answer really depends on your wyern's physical characteristics. We seem to be dealing with a bulky wyvern: strong, with a nasty-looking club for a tail and nice wide wings with clawed hands at the ends. Your spiked ridge along the spine is unfortunate for any idea of riders, but not insurmountable if you get creative. Not that I can see how these could fly at all (not with the pesky square-cube law being the bane of dragons everywhere), but you concede that they won't be doing more than gliding; I'll assume they can leap high enough to glide for at least a couple of seconds on level ground, even if they can't actively gain altitude without very favourable wind patterns and a good launching point.
Given their general build, close formation fighting would be absurdity. You won't be getting any good shield walls here: their bodies just won't be able to make a tight formation effectively (what with the wings and tail doomed to stick out everywhere, which will likely move on instinct as well as on command), never mind that they don't look like they could hold a suitably oversized shield very well. However, you do have a promising basis for individual juggernauts, or cavalry squads if they can move quickly enough (I'll assume they can, or they would make lousy hunters in nature). If the terrain is favourable, you'll also have a sound basis for hit-and-run tactics with bows or diving strikes from above.
For a juggernaut, you'd want nice solid armor. Full plate would be extremely expensive and difficult to make in a way that would be effective, so I'd suggest chain mail instead as the baseline, and plate armor only for critical points. A nice thick layer of that, and the dragon's body will be pretty close to impervious: armoring the wings with that isn't practical unless they can fold in enough to let the body armor pin them against the body (which would be problematic for other reasons), but punctures in the wings shouldn't lead to fatal blood loss. More practical would be a protective lining along the wing edges to deter blades trying to cut into them. You could add a few spikes to that lining and make the wings into very nasty sweeping weapons, but that depends on if the wings could handle the force needed to cut through potentially several humans at once (or at least to rebound with minimal damage if they hit more than they can cut through); if they can't, trying to scythe through enemies would cause horrendous damage to the wings or even rip them off entirely.
Whether or not that knife-wing idea would be viable, your probable weapon would be an axe or sword. Their wing-hands look badly arranged for effective use of a spear, and those are mostly anti-cavalry in any case (I'm assuming your wyverns are at least the match of a horse in size and strength, rendering anti-cavalry weaponry unnecessary). A sword gives you more maneuverability, and you'd last longer in a fight before tiring, but the weight of an axe-head could let you chop through multiple foes in one heavy swing if your wyverns can put enough force behind it. The tail would make an excellent bludgeon, although if you're using it you'd better keep a little distance from your allies. Add some sharp edges if you like, to make sure it can cut through things instead of just breaking bones, but that tail doesn't seem to have the maneuverability to focus on using the tip: it's a blunt instrument, so wield (and ideally armor) it accordingly.
These would be individual fighters: certainly with more than one on the field at a time, but as I pointed out earlier these wyverns won't do well in formations. They'd be vulnerable to being surrounded and dying of a thousand cuts, but a few of these would smash a shield wall to pieces by sheer force. I think it goes without saying that these guys will be lucky to glide anywhere without hitting the ground hard enough to break bones, so they will be firmly grounded.
There are various kinds of cavalry: shock, light, lancer, and probably a dozen more that I can't recall. Covering shock cavalry here would probably get you some minor variation on the juggernauts, so let's try light cavalry instead. Chain mail is going to be too heavy to allow a high speed; it might be added to reinforce key weak points, but leather is your probable choice for armor. The knife-wings I mentioned earlier, if viable, would be an excellent idea here: cavalry wyverns won't be charging head-on into tight formations unless they have a death wish, but those would do horrific damage if they flanked a group successfully.
For weapons, you probably want a good long sword. A standard spear would be ill-advised, but lances with their reach would be useful for a devastating charge as long as you remember that they were a liability in close combat. You would either charge-retreat-charge-retreat in a cycle, or charge once and discard the lances in favor of swords for the ensuing fight in close quarters; the latter would recommend heavier armor, because at that point you basically have shock cavalry.
Little to no armor would be advisable here, since you need to maximize speed and agility. If you have lightweight silk available in great quantities to stop arrows, great, but that would be hideously expensive. Wing protection would only weigh them down, and these guys will want the option to glide away.
Bows will be your weapon of choice here. If they have the strength and training, I would advise the longbow or a similar weapon, but those were not mastered quickly: the famed English longbow often required years to build the necessary muscle strength and stamina to use it effectively, to the point where it was at one time a royal decree that all men had to train with bows regularly. Still, it would fit their stature (I'm assuming that your wyverns are at least the size of a horse), and that weapon did not gain its fame without good reason. If you doubt your wyverns would on average be capable of using the thing, crossbows have the firepower to make a good second pick; slow to reload, but if you are harassing a slower enemy that doesn't matter much.
Tactics would be straightforward: your wyverns would be using their greater speed to fire and withdraw, picking away at the enemy's strength over the course of an advance. If your wyverns can manage greater draw-weights for bows than humans, all the better: you'll have more range. If the terrain is suitable (the enemy is marching through a narrow valley, ideally, but in general anything with high hills or mountains will be useful), gliding down and firing from above would cause tremendous disruption without any real risk; bonus points if your wyverns have some equivalent to Greek fire or napalm together with a few fire arrows.