Tips are hard if I don’t know you and how you draw. So I’ll just launch some general tips for everyone: the most important thing for me is to enjoy and appreciate what you draw, so you have the endurance and motivation to keep practicing and studying to get better. Practicing and studying costs time, so pick what you want to learn carefully! And don’t forget that getting better takes even more time.
Some core fundamentals are:
-Basic shapes
-Anatomy and construction
-Light and value
-Perspective
-Colour
-Composition
There are guides and books on all of those topics but I wouldn’t study it all at once. Focus on what you want to improve on first. For cartoony stuff I’d focus on basic shapes, basic anatomy, colour and light/shadows. Don’t forget to study from life objects as well! If you get stuck on something complex, for example the hood of a hoodie folding over the shoulder, look at a real hoodie and you can see for yourself! (I see so many artists who draw the pullstrings coming out some random spot on the chest instead of out the hood, smh!)
Next to learning your fundamentals, you’ll need to learn how to use your program (or medium/tools irl): figure out ways to apply what you learn in your own way. There are multiple ways to do lineart, but some artists don’t use lineart at all! Find your own niche. This takes experimentation and practice too. Eventually the whole mix of quirks becomes “your style” but I would not focus on sticking to one method during your beginner phase, stay experimental.
I use “painttool Sai” for most of my art, though I’d recommend “Clip Studio Paint” over Sai, it’s better in general and all the new kids are using it. Learning photoshop and other programs for extra tools and effects can never hurt.
If you need more help I’d suggest taking a look at this page:
https://hubpages.com/art/how-to-draw-learn
Have fun :)