I'm looking through Ozle's card list, here are my thoughts. Note I'm not thinking overly carefully, so there's a reasonable chance I'll miss things.
Thieves!:
Thief, Money Lender, Cutpurse, Festival, Lighthouse, Loan, Village, Market, Masquerade, Expand
Looks like an okay, moneyish set. I guess the theme is more thematic than trying to make thief good here (there's too much virtual money for that.
Gardens:
Garden, Bureaucrat, Talisman, Workers village, Warehouse, Adventurer, Cellar, Woodcutter, Hoard, City
Some decent Gardens supporters here. I think this would mostly be a Gardens rush type game, as the name suggests, which is fine. I guess you want the story to really highlight Gardens.
Pirates: Pearl Diver, Merchant Ship, Pirate Ship, Lookout, Bazaar, Rabble, Treasure Map, Workshop, Remodel, Chancellor
Pirate Ship could maybe be good here, it's got the stuff to draw into and play multiple times per turn, but no extra buys. The set looks generally okay though, I don't see any obvious cards/combos.
Wharf: Wharf, Fishing Village, Cellar, Council Room, Bank, Market, Chapel, Ironworks, Monument, Thief
Highlight Wharf/Fishing Village, I guess. There's plenty of support to make it do big, bad, scary things as well.
Trade Route: Islands, Gardens, Trade Route, Hoard, Village, Lookout, Sea Hag, Ambassador, Throne Room, Bureaucrat, Colony & Platinum
Yeah, Trade Route could quickly get good with both Islands and Ambassador. This board seems to have some really obvious stuff you want to do, but it's not easy to work out when and how you want to do them. Warlord Bot would probably work here?
Right, that'll do me for now. I think all of these could work as sets, basically.