Really, there is no such thing as a DMR under $200. There are only a few guns that are already good enough to be counted as DMR's, but they are well over $200.
Your best bet would be getting a CYMA M14 and upgrading from there.
I'd recommend these simple, upgrades for your CYMA M14 to start out:
- M125-M130 spring
- Prometheus Tight Bore
- Tokyo Marui Hop Up Unit
- KWA 2GX bucking
- Very high quality .28G bb's
- Teflon Tape Hop Up Mod
- Re-Shim & Re-Grease
- New O-Ring (#14 is usually the correct size, but not always)
- A good 9.6V battery