My advice would be to start with a pair of something decent within your price range, such as B&W 303 (my favorite) or Paradigm or whatever sounds good to you for your mains. Use whatever used speakers you can get your hands on, borrow, steal, whatever, as surrounds and center. Or go without a center.

As money becomes available in the future, add new matching speakers as surrounds, or maybe something bigger and better as mains, and move the mains to surround.

Everybody thinks I have a killer system. I am still using 15 year old Boston A40s as my surrounds, with one woofer not working. I only just bought a subwoofer this weekend, a used SVS, and I built my center channel from scratch. (except of course the drivers). My mains are 14yo Spica TC-50s.

My speakers are cobbled together, but it all sounds great, better than most of the demos I hear of the lower priced stuff in the stores, and this stuff will still cost >$1000.

As for DIY, if you have any woodworking tools and skills, it may be a good way to go, if you can wait for the results. I had to buy most of my tools to build my center, but now they're waiting to be used again. Maybe I'll build new surrounds. The results far surpass what you would get new for the same money. You really can build some high-end type equipment.