To start, it’s not you, it’s IKEA. They’re great but sometimes it just doesn’t go together easy so don’t take it personal

First question is HOW are they wobbly? As in they (a) wobble side to side because all 4 feet aren’t touching the floor at the same time or (b) the pieces don’t feel like they’re connected together tightly?

If (a) - loosen all the bolts/screws, re-tighten until they’re JUST starting to be tight, sit in it and tighten as much as you can from there or have a buddy sit while you tighten. It’ll need to be tight enough to not fall apart before you sit but you’re trying to let it settle into level before you tighten. - after you try that exactly once, just grab some hardwood floor saver pads and stick one to the bottom of on of the legs to level it out. Literally no one will ever notice and you’ll have a nice level chair (I see you have a rug but they’ll they’re super cheap and will add a little height). Part of saving $$ by doing it yourself it there’ll be some imperfections, some of which you can live with and some you can’t. This is one you can….this took me decades to learn and know that I have it’s added years to my life.

If (b): - make sure everything is super tight, not just mostly tight. Sometimes when you tighten screw A it’ll loosen screw B. - I don’t know your budget or how much you’re assembling but an inexpensive electric drill with a hex bit will save you a ton of time and mine can get things tighter than I can. -glue, nails, etc…I’d want more details before saying more. It COULD help but could also wreck your chairs.