It might be worth your time to look into "stepup rings". These are threaded adapters which convert a large diameter filter to a smaller diameter lens. So if you had two lenses which take filter size 58mm and 67mm, you would buy the larger size filter and a 58 to 67 stepup ring. Now one filter can be used with both lenses. Not as convenient as two separate filters but certainly less costly since you seem to be just starting out with a SLR system. Good luck.
Not a big fan of step-up rings, at least not for the "UV Haze" type filter that resides on a lot of lenses. Part of its "job" is to protect the front element from impact and damage. I recently dropped my 70-200 f/4 IS in an asphalt parking lot. The B+W 010 filter shattered but stayed in the ring. I was able to get it off and there was no damage to the front element. There was some internal damage but it would have been worse had the front element shattered instead of a filter.
I suspect I could have had a 67 -> 77 step-up ring and a UV Haze on it. This way I could use the 77mm circular polarizer that I had when I bought the lens, but the impact might well have damaged the ring and left it, at best, stuck in the threads.
I understand the appeal of using step up rings, but the OP is going to have two lenses. If you believe the results at http://www.lenstip.com/113.4-article-UV_filters_test_Description_of_the_results_and_summary.html
the Hoya UV filters beat B+W slightly. A Hoya HMC UV filter is $19 at Amazon right now. A 52 -> 58 step up ring is $4. And then he might want a replacement cap. I'd buy two filters. Consider the difference to be full time insurance on both lenses.
Some caveats. This is a new user (based on this and his other threads) and I'm speaking only of protection/UV filters. If he wants to use a polarizer or something more expensive his decision might be different, but by then so might his lens choices.