branded merchandise

Hello: There's always Amazon, but wondering if maybe some other affiliate programs may be better for Halloween-related stuff ala SpiritHalloween.com ALSO: Is it a big no-no to work with more than one affiliate with one website? If they're getting click-through sales why would it matter? And...

who is the best to use for dropshipping custom branded merchandise? I want to do tshirts, mugs, and possibly a few other items with my branding. I think I've heard teespring is good, but just for shirts? is there one that is worth having do it all, or should I do shirts at t-spring and the rest...