Illustration softwares like Canva, Stencil and Pixteller are good enough for basic stuff. I am actually quite bad at free hand vector drawings, so I try to keep my designs simple and clean, and leverage on nice pics (stock photos that don't need to edit), good font combination and icons (flaticons.com).

There are many sites when it comes to copywriting, like Neville from KopywritingKourse, Neil Patel, the Appsumo team, The Hustle.co are a few good gurus and examples. Copywriting involves you understanding the reader's psyche well, so you can "connect" better with them. Sadly, copywriting is a very hands-on skill and can be very subjective as well. A good practice is to constantly be on the look out for banners and headlines, and ask yourself if you can come up with 3 different and better ways to word it. That's a good mental exercise.

Don Miller from 5minutemarketingmakeover.com, through not a copywriter per se, has a very good approach to coming up with brand messages that "sticks".

Aim for clarity, then sexify it.