Any specific requirements for higher frequency (or even RF) or arb waveforms?
With the $300 pricepoint, I think you're right between the more entry level sig gens and the more fully featured true arb ones... and if you don't have a specific need/goal in mind for what you're looking for... I'm wondering if it would just be better to get a real cheap DDS generator for now and just save the rest for an eventual upgrade when you have more money or have a better idea of what you're going to be using it for. That said, if you don't have an immediate use, maybe you'd be better off saving a bit and going for a good all-arounder like the SDG2000X series (I've got an SDG2082X and it works great, though the fan is a hair loud).
Building your own is a great option, but if you want to use the generator to test parts or performance, it's going to be much harder to do since you're going to have to get the performance of your design up to snuff before you can go testing other things.