For that price, go with a wire-feed welder (what you'd consider a MIG), but just use flux core wire, instead of worrying about a regulator and tanks.
You can get one around $300. Try
www.toolking.com, for hobarts.
I personally used a 110v Lincoln wire feed for many years, with good results.
If you are using a 110v welder, you can do most anything you need on a Jeep or other 4x4, other than heavy things like welding spider gears, and thick weld-on D-ring tabs (In my opinion, anyway).
The key to success with a smaller welder is:
1) Clean all metal well
2) Get your joints tight fitting. Don't try to fill gaps with weld.
3) Bevel the joint edges, that lets you get a bit further into the metal for better penetration.
4) Design things with extra weld area when possible for critical stuff. For example, I make my own D-ring tabs that are long. I cut a rectangular hole in both sides of the bumper tube, and run the tab all the way through. So its welded on the front and the back surfaces for more strength.
Flux Core wire in 0.035" is what you want, for the best possible penetration from a 110v machine. I still use that on my 220v lincoln.
Miller, Lincoln, and Hobart all make good 110v wire feed units. You can find them often on ebay from someone local for $300 or less, especially lincolns, as they are the most common. Home Depot sells consumables for Lincoln, the Miller and Hobarts will require you to go to a welding shop to get tips, usually.