Probably the easiest monosynths to learn would be the Roland SH-101, Arturia MiniBrute or MicroBrute - but those don't have presets.
The Novation Bass Station II is fairly easy to learn and has presets and arpeggiator. New: $500, Used: $350ish.
Might be hard to find an analog polysynth with the features you're looking for in the $500 - $600 price range. Korg DW-8000 would come close, but has digital oscillators and analog filters. No sliders for easy editing, so you'd already need to be familiar with subtractive synthesis.
There are several virtual analog polysynths that fit the bill. I've bought a used Roland Gaia a couple of years ago for under $400.