There are quite a few in your price range to choose from, it's going to be a long & hopefully fun research journey.
Lately I've been smitten with the Lab by Atmizoo. It's a really clean, ergo dynamic, beautiful mod. It has a lot of unique qualities that you just don't find in other mech mods, yet it's quite minimalistic at the same time. I love mine, it's a keeper.
The Nanos by mmvapors is getting rave reviews. I have it at the top of my wish list. I have their Poldiac and love it.
The Nemesis by Atmonixani is highly touted. I love mine.
There are tons more, of course. My favorite mod of all of mine so far, is still the Roller. It's just the perfect fit for my hand, in weight, height and circumference. It's easy to change the battery sizes, unlike most mech mods where you have to change out a tube or add a spacer. But the Lab, Poldiac and MicroChel all vie for top honors too. The MicroChel is just a terrific little workhorse, so stealth and comfortable. The coating on it helps keep the winter chill off which is a big bonus.
I'm a side button fanatic, because I have a pet peeve with bottom buttons that don't sit right on the table. LoL, but that's my pet peeve, not the norm. Not all wobble or lean, of course. They're really easy to clean and change springs or magnets out.
With that said, the copper tube mods seem to be the rage right now, due to hard hitting low voltage drop. There's quite a few to choose from. As with all mech mods, make sure you get the right battery, with the right amps.