I also currently have a T-foil, and it's still in my kitebar bag, for messing around in marginal winds waiting for the wind to pick up, or for letting other people mess around with. I've also used it at spots when I'm visiting for the first time, I put it up in the air and fly it around to feel the steadiness of the wind.
I also (recently) had a 3M Waroo LEI, which was fun, could be rigged to my high wind kite bar, and is fun for skateboarding, but the kite is super squirrely and tricky to trim due to its small size.
When I started, I got a 2.5M stunt foil with handles from ebay. It was fun, and helped me to get acquainted with the wind window, but the handle experience is far different from having a bar.
I then stepped up to a used 6M naish boxer (back in 2005) and flew it on the beach in 10-15mph winds. Flew it a lot and learned a lot. I would recommend the same. Gets you used to the harness, rigging, pumping, lines, launching, the whole lot.
Things I learned from this kite that are invaluable:
simulating waterstart by sitting down and diving the kite
how to keep the kite in the air in marginal wind
how to relaunch the kite
getting an intuitive feel for the power delivery from the kite's position
quick release system practice
depower and sheeting
Flying kites is fun, even if you're not riding. If you want to go the whole hog, get a foil trainer for convenience of setup, then a small LEI (4-6m or so) for real simulation.
Also check out
for shieets and giggles