TM M4A1 New Type. It ran stock, it ran upgraded to 380fps....ran perfectly until I tripped and fell on it...breaking the body.
I now have 2 PTW M4's, 1 King Arms Galil and 1 WE M4 AWSS/WETTI gas rifle.
I wish I had started with what I now have instead of cycling through all the dozens of rifles that I bought/sold/traded over the years.
In the long run...you really are better off saving up for the best rifle within your budget. The going rate for a really solid rifle (M-series/armalite variant) is about $600-800.
But...I can completely understand the position of starting out with something to try out the sport...and not wanting to invest that much if you're not going to be into it for the long run.
However...a "cheap" gun will hold little to no resale value. If it's worth anything it'll be significantly less than what you originally paid for it. Higher end guns will retain their value better.
As a bit of an aside...you look and feel like a tool if you head out to a game with a sub-par marginal piece of crap. And then you really look like an idiot when it breaks in the middle of the day and you're left sitting there with your thumb up your ass. Not to say a gun has to be expensive to work...it just has to work well and reliably...and quite often you get what you pay for. That said...you feel just as bad when a $$$$ PTW craps out on you at a game too.
Best of luck,