Lots of OOTers have recommended the stuff from this site:
Upton teas
They have some cool starter packs. The site design can be funky on them and it can be hard to see all the starter packs at once sometimes, but whatever. It's a cool site and mostly the navigation is fine. I still have a ton of green tea to work off, so I haven't tried it yet.
I do agree that loose tea is probably going to be the best. I have some loose green tea and it tastes way better than the various bagged kinds I've gotten over the years. The other kinds of non-bagged tea I've gotten have so far all been notably good too. So, it seems pretty worth it to me. The flavors I've had so far have some more, I dunno, roundness or fullness or something. You feel like you're drinking something richer, even if it's not necessarily stronger.