I live in a sailing hub. A bunch of sailors that want to race have taught themselves to foil after only a season of kiting on a TT. There have been about 4 or 5 now. All pretty young and keen. A few are now racing competently.
Kite control is the biggest determinant. After that its paramount to be a decent swimmer (read: efficient and easy body drag). All of the aforementioned new foilers have done their fair share of swimming in with a wet foil kite. Most learned to tt with an LEI, and then got a foil, and then went to foil kites. These guys had designs on racing hydrofoils with foil kites from the get go and switched from TT to foil and from LEI to Foil kite as early as soon as they felt confident.
Looking at their progression and remembering my own, I would say:
Stay disciplined with your choice of conditions. Once you crack it, you can challenge yourselve with tougher and tougher conditions, but for the first while learning to foil. 11-15 knots and not too choppy/cold/weedy/etc. You can keep using the TT when its too windy to learn to foil, but if you really want to foil take every appropriate opportunity to struggle with it, despite giving up riding time.
An appropriate learning set up can speed up progress and minimize pain and frustration. A short mast, a big wing, a big ol Alien air type board and a 10-12m easy to fly/relaunch LEI are the best recipe. I've seen a few learn on full race set ups. Doable, but much harder.
Spend some time on this type of balance board:
https://images.app.goo.gl/XAMwQoQAZdHSSYas5
I made mine out of an old skate deck, a piece of PVC and some duct tape. It will help you dial into that very small and mobile balance point while evening out the foot pressure making it easier to go from rear foot (TT) to front foot bias (Foil).
Have fun.