Depends on budget - but if you want something that packs a punch take a look at the Nemesis. I'm assured the Poldiac is good too... silver plated brass contacts so I'm assuming it's 'up there'. I'm actually getting my hands on one for review purposes tomorrow, which I'm excited about!
Exotic ones DO cost, but the only thing that really matters, if performance is the priority, is the quality of the contacts. That's button, positive, negative and 510 positive contacts.
If money's an issue the Drawtube Smart is highly versatile. The contacts are plated brass, so it's easy to squeeze more performance by lightly sanding the delrin threaded screw (battery positive and centre post - all same piece), and also the base of the button.
For your first mechanical, I'd probably start around that end of the market and see how you get on. A lot of people don't like the performance tail-off as the battery starts to fade... but if you want to build sub ohm/ohm
coils then 0.3/0.4 volt drop off is noticeable, but still a lot punchier than the vape you can get off some VV
devices.