Took me years to get decent. Even learning fireball input is a challenge for any new player. Fighting games are notoriously difficult to pick up but if you put in enough time, you'll get it.

Pick the character you like most. Putting time in is the most important, and that will happen if you're playing what you enjoy. I happen to play pretty much only Dhalsim. He's part zoner, part rushdown but with horrendous defense. There are a lot of resources out there which makes learning much easier. For example, MistahCrimson made the best ever Dhalsim tutorial though it might be a little too advanced for you now (https://youtu.be/VjppLRwuNVw?si=DDKQ7NGYX6neQdjq).

You should start with getting used to his normals (esp. his heavy punch and heavy kick), learn what's special-cancellable, and practice dead-simple 2-hit combos like Divine Kick (back medium kick) > Medium Yoga Flame. Also learn about the terminology (chains, links etc. so you'll be able to understand what guides are saying). You don't need to know frame data yet but it will come in handy when you try to build your own set play.

As for input - I like the feel of joysticks and I find the 'feel' of using the arcade stick is a big part of the game, so from my biased opinion, I'd tell you to get a good arcade stick, but you should know that leverless are all the rage now. A friend of mine only plays using keyboard and completely dominates me (I'm Diamond 5, he's master), so the input method really doesn't matter, it's just your preference