Screen Printing is probably your best bet. It has the best feel to it, and you can achieve extraordinary amounts of detail with it. It's messy, and time consuming though. And, has a high learning curve. You may want to consider having someone else screen print your designs for you, save you a lot of money, time and no mess.
DTG allows you to do one-offs, which means you won't have to worry about printing tees in advance that may or may not sell. On the down side, the
DTG machines that use the white ink are notoriously problematic, and require everyday use to keep the white ink heads from clogging. Plus, the upfront cost is a big risk, especially if you're small-time.
Vinyl, like
DTG, allows you to do one-offs, so you won't have to print a design until someone orders it. It's cost-effective, easy to learn, and only requires a vinyl-cutter and a heat press. On the downside, you're usually limited to 1-color designs, the vinyl does have a "plastic" feel to it, that can sometime even "wrinkle" if you fold it, and you can't print designs with a lot of detail. Your designs would be limited to really a "block-like" feel..
Personally, I would go with Screen Printing, but that's just me. My first t-shirt company, I used vinyl. I've since shut it down, not because of the print method.. various mistakes I made that I won't get into here.. But, I will say, with vinyl, you're very limited in your creativity, and the feel of vinyl is often unpleasant.
What is the most effective way to print shirts for a online business? ? 
Re: What is the most effective way to print shirts for a online business? ? 
