Beginner in Graphics

Hey everyone, I just finished my AA and have found myself really interested in graphic design. I've played around with very very basic editing tools like Picmonkey (lol oops) for my college ministry and I have been given the opportunity to help out to create new designs for my church. I was wondering what you guys would suggest to use online that is free or affordable for a beginner. Also, if it is Mac friendly, even better! Thanks everyone! :)

P.S. I'm sorry if this question has already been brought up before