Cheap but good tires + TPMS will run you 1k. Then you have 2k for wheels. You can get brand new set of CH with that. (good wheels + cheap tire combo)
You can buy great tires +TPMS for about 1800, then buy cheap but good (enough) wheels like VMR V710 or V713. (great tire + good enough wheel combo)
Wait a bit till you find a good local OEM 19 FS thread.
OEM 19s are forged and lighter than your OEM 18s. And most likely it will come with great tires (PS2). That would be win win if you asked me.
I went with option 3. Final cost? About 400 total.
Bought under 3k miles OEM 19s for 1800. Sold my under 3k miles OEM 18s for 1500 (but gas: 50, paypal fee and etc: 65)
PAST: 11 E70 X5M | 08 E90 M3 | 08 E92 335i | 03.5 E46 M3 | 99 E36 M3