>>54233103Obviously you need to just start.
For resources, Wolfey has some pretty useful videos on competitive pokemon you can check out. He is often considered the GOAT for a reason. His videos can be really helpful, like the ones of tournaments that he participates in. They're pretty entertaining and insightful.
Wolfey, along with many other top trainers, also made a website to help people learn more about the competitive scene! It's great. If you're interested in it, I would highly recommend it. It's called vgcguide.
Personally? I would say to avoid singles. They're just a lot less fun most of the time. Frustrating stuff like snowballing and stalling, is a lot more prevalent (and effective) in it.
Doubles/VGC are much better imo. Faster paced, makes you think on your feet a lot more. You can make much more interesting team comps too. Also, the matches are a lot more volatile and dependent on YOU and your opponent rather than the pokemon that are used.
It's important to know that team building and knowing how your pokemon interact with each other is a BIG part of competitive doubles, but I would say not to worry too hard on what is viable and what is not in the beginning. Obviously theorycrafting matters, but if you are good enough and smart with how you build your team you can beat a lot of trainers with what people think are "shitmons".
Don't restrict yourself to only playing OU and using OU pokemon.
If you don't know where to start, why not just do random doubles or random singles on smogon? You and your opponent are given random pokemon and battle each other kind of like gen 3/4's Battle Factory.
Have fun and good luck!