To answer your questions.
Foils are optional not necessary. (for me only they are too slow and have wing stability issues i don't care for this only MY opinion)
If you go the foil route and want to move to water make sure to buy a closed cell only. otherwise any modern day inflatable will do the job year round any discipline you choose.
By your description of experience you sound like your on a path to get seriously hurt especially on larger traction kites. Please take the time to at least try to find a kite instructor and take a few lessons this is repeated over and over for a reason.
(if you have no other choice fly only in light conditions and keep it static for awhile until you can fly with your eyes closed and ease into flyin the kite with a board and ski's USE EXTREME CAUTION if you are on a icy lake one accidental jump can leave you in the hospital seen plenty in my day.)
what style of ski's etc? (whatever is cheap or free and stays on your feet. If you have little downhill or actual sking experience the expensive stuff won't make you better.)
Kite reccomendations are a waste of time and more then likely to end in a pissing contest as is debating foils vs inflatables. Wise advice is avoid these topics all together.
Demo if possible as it sounds you already have. Try to find as many as possible to demo and try.
Try out the foils and all the inflatables.
Look for a push away release system. More depower the better. Any modern day kite 2008 or later should do the job. Keep it cheap cause your gonna thrash it learning. Just don't cheap out on safety.
hope this is what you are looking for.