I definitely want an L series lens because they will last but what is the cheapest one...
I think we get a little too wrapped up in thinking L lenses are the only ones that last. I've had a 24 f/2.8 and a 35 f/2 for 16 and 15 years respectively. Many shots on them, been mountaineering and backpacking with both many times. They still work just fine. No, they aren't as sharp as some other options, but they sure are small and light. I've also had many wide L lenses, including the first 17-35 f/2.8, 24 f/1.4, 35 f/1.4, 24 TS, 16-35 and 17-40. In fact, the only Canon wide angle I haven't had at one point or another is the 28 f/2.8 (do you think I have a problem??).
Too many lenses with too many problems. Is there a lens I can afford without saving up for far too long? Should I stick with primes when it comes to wide angle lens?
Generally true with Canon wide angles. I currently use the Zeiss 21 and Zeiss 35. As others have mentioned, I believe these two are the best glass, but they are insanely expensive and manual focus. They are the ones that will come close to "getting the most out of your 5DII," which is the Canon camera I use (well in addition to the 24TS L II, which I certainly wouldn't recommend for you). Frankly, if you are handholding while shooting, I think camera movement and focus inaccuracy will show in the images much more than the difference in sharpness between all the wide angles mentioned above. You are going to get all sorts of opinions, so I'll give you mine: Based on some of your other posts, it seems like you are on the newer-end of your experience with photography but have a great desire to learn a lot, which is awesome. Get a prime in the focal length you want. Don't worry about sharpness, how robust it is, or even what it's max aperture is. Photographers use wide angles in so many different ways. Find out how you like to use it over the course of months or years, then jump to other lenses as you learn.
Dave