There is a tried and true method of learning how to get started in this game. A few steps:
1) Pick a character to learn. Ignore tier lists and public opinion, avoid tech-heavy characters like spacies for now.
2) Watch videos of the best player of that character, note which moves they use and ask yourself: "Why is he/she using this move over that similar move?"
**After this step, you need at least one other human player who is going through the same steps to practice with**
3) Learn the basic tricks of the character via the videos, then imitate them. For example, If your Ivysaur uses dash attack a lot and the best Ivysaur player never uses it, try removing it and replacing it whatever that player would use in that situation, like ftilt.
4) If you are not winning, ask yourself: Why not? If possible, look back on your matches via recording and see when you got hit. If you are having trouble winning after you complete this step...
5) Compare your matches with step 2's videos, and repeat the process.
This works a lot better when you have more friends to play it with. The more diverse your matches get, the more experience you will get and the more bad habits you will stop forming.