https://www.*******.com/playlist?lis...5oBsdfMpaIZlsB
This guy, Callum, has helped me tremendously and personally at PAWN scripting. In fact, I can't actually thank him enough. He has a you-tube series which covers many different systems such as Registering/Login, Leveling, General Commands, Player Spawning, House System, Damage System, Vehicle System etc.
Sure, follow his guide as he writes his code, but that's his way of doing things. Every coder, in my opinion, has their preferences and different solutions of doing certain tasks. Analyze his code, understand what each thing does, experiment, mix it up, refer to the SA:MP Wiki, put your own twist on it, try re-building it by memory, learn the syntax, functions, etc.
If you're ever stuck, he even has his own Discord server in which has proved exceedingly helpful for myself if I have an error I just can't get my mind around.