On that budget, these are some things you might NEED depending on what you're up to.......here's my three cents:
***Mic Preamp - depending on the interface you have, you might not need to pay for this...yet.
***Recording Monitoring - (headphones, mixer, cables) make sure you can hear everything you need to hear when Recording, WITHOUT letting the Mics hear it. I recommend having a second mic setup into a mixer - one mic to Record and one mic to monitor in headphones. (This is very important if RECORDING is your thing and you're stuck using your DAW to monitor - the digital realm presents horrible latency issues that make the "Recording vibe" very difficult to obtain)
***Recording Booth - do you have the space? This seriously saves lives.
***Large-Diaphragm Condenser Mic - this paired with a popshield will mean A LOT LESS EQing
***Control Surface - check out the Behringer BCF2000
, also M-Audio Keystation 61es for your price range...you will fall in love.
***DI Box - very necessary if you want to record Keyboards or other direct instruments (even guitars).
***Subwoofer - if you don't already have one, this may or may not be essential depending on your project types.
***Better Computer - depends on what you have!
***Bigger/Denser/Additional Computer Monitor - you need to see what you're working on comfortably, and it needs to not slow you down.
***DAW - do you even have one? I recommend Ableton if you have the money, but that is nothing more than a personal preference.
***Outboard Gear - Compressors, EQs, Effects, etc... I wouldn't waste tooo much time with these if you're using a DAW. Wait until you have a lot more than 250...then it will be well-worth-it.
***Nice Chair - perhaps the most important piece of equipment in any Studio
I know I'm forgetting something, but there's some stuff to look at. Again, it all depends on what you'll be doing and what is most important for your functionality. :D