Congrats on getting a TG16. Sad thing is it's a bad time to be getting into the system if you are wanting to acquire actual US HuCards, but don't let this deter you. There's still deals to be had for games you mainly want to just play and enjoy. Think about getting your TG16 region modded or a better route just get a cheap pc-engine for the imports. There are so many good imports that are easy to play and require no knowledge of japanese to enjoy. There's also an Everdrive route which I'm sure you know about already, but is really not for this topic. So, for some decent priced HuCards:
Bomberman
Bonks Adventure
Bonks Return
Neutopia
Ninja Spirit. (game is not worth what ebay says)
Battle Royale (can be fun with friends)
Bloody Wolf
Boxy Boy - (fun challenging puzzle game)
Cratermaze
Alien Crush
Dragon's Curse
DUNGEON EXPLORER!!!!!!!!!!!!!!!!!!!!!!! (fantastic music)Dungeons and Dragons - Order of the Griffon
Fantasy Zone
Dragon Spirit (yes a shooter but amazing just for the music)
Space Harrier
Hit the Ice (fun hockey game that's 2 player)
Final Lap Twin
JJ & Jeff
Power Golf
Legendary Axe I & II
Plenty more but others will chime in. For more info on games please check out
http://www.pcengine.co.uk/