Tropical Fish Keeping - Aquarium fish care and resources

Hey, I'm kinda new on here (posted something about a disease a while ago, but that's al)
I'm 15 years old (almost 16 :-D, 13 dec.)
My name is Judith, and I started keeping fish about a year ago. (although at first I had about an 2/3 gallon :oops: tank)
I probably did a lot wrong, but one of my first fish is still alive (although she seems to be having troubles with old age).
A while ago a combination of an unknown disease and fin rot, with Ich Spots as the finishing touch :cry: killed about all my fish, so I started anew, cycling and adding new fish.
I know about some basics of fish keeping, but altogether not much. So I hope You guys can help me keep my fish alive and happy :-D