The main thing is to go ahead and start trying things before trying to figure out which is the "best" way to go first. I got stuck in that mode for years. The learning curve is huge no matter what so you might as well dive in and get going. Be prepared to make mistakes. It seems that even if you have somebody to help with marketing, you are still your own #1 marketing manager, 24/7. It's a lot of work.
I'm going the online route first. I'm learning eBay, Etsy, ArtbyUs and other online art selling sites as well as marketing by blogging and Squidoo lenses, not to mention just exactly what my artistic style is, all at the same time. And, finally, at long last...I'm having a blast. In my first month on eBay I've sold only one piece a week, but it's a start. I suspect it takes a while for people to see your name and trust that you're going to be around a while before they start buying. (Or maybe my art ain't that great. lol)
I can also see now how getting in an real life gallery would feed back into the online aspects of the business, and vice versa. Helps people to be able to go back and forth and see how much work you're putting into it. Here in my part of Iowa I'm lucky to be near several funky galleries and I think none of them have ACEO's (artist trade cards made for sale). I think that's probably my niche.
Now I should stop talking and get back to work! lol
Gretchen
heArt-a-Day