Canva is by far the most user-friendly, sleek, and customizable graphic-design tool that I’ve ever used. I use it for ALL of my social media promos, business cards, printed materials, and love both the desktop and iPhone interface for designing Instagram promos for both the stories and the feed.
I went with 99designs for my podcast logo and was very impressed. The quality of artists and designers who chimed in on my logo concepts was so impressive, that the most challenging part was having Too many great options to choose from.