Hi from Nico (nakaniko), Venice Italy, I'm a snowboarder and windsurfer since about '96. Having started in the wrong way in snowboarding (175 cm hard old board, left knee not far from broken), I carefully looked for the correct board to start windsurfing, a big board with daggerboard.
Learning windsurf is not so difficult imho, but you have to keep in mind that at the end a windsurf is not far from a sailing boat, at the beginning. So you need a wide and stable board, the better are the ones of the rental and school centers, with a 90-100 cm width and a big volume. I keep on telling to friend who wants to try that an absolute beginner has to step on a board wide more than his weight in kilos, and with a volume much more than the double of its weight. Yes you could buy a modern wide-beginner board, but they are not so cheap and you will be bored of a such big and fatty board soon, looking for a smaller and more lively freeride board.
Believe me, the progressive but slower learning curve of windsurfing imho is a good thing, a lot of exciting steps, you will understand what I mean the first time your board will start planing over the water surface, and the first time you wind will pull you up from the water in a waterstart...
BTW my progression has been: 175 lt with daggerboard, then without daggerboard 138lt, 125 lt, and now various boards from 95 to 257 (Serenity) but mainly a 98 and a 112 lt
About sail: start with a freeride sail without cambers, light and small, if you want to buy a 6,5 if you are about 80 kg, but use it at the beginnign only with low winds under 10 knots.