There are so many good options nowadays, it's awful hard to make a choice.
For flavor and ease of use, a doggy style clone (they have a topfill version now which is nice) from FT. They are fairly adjustable and to get them to leak you have to split a plastic tank or something (which I have done, actually) but they are non leakers.
The ephro true is fantastic, a bit trickier to get wicking right, and a very MTL vape. It has a bubble tank for larger capacity but I'm not sure it's needed. This sucker does not burn through a ton of vape. Airflow pretty darn closed off.
The Siren V2 is a super easy atty to build at first, won't break the bank. Too airy for some, personally I run it airflow wide open and it's more of a restricted lung hit. I LOVE this atomizer, it was the first RTA I bought that didn't leak everywhere (to be fair, I also switched to rayon around that time.)
Cthulu mini: nice. Again, airflow options sort of restricted. Good flavor tank.
There are about a jillion others. I must say, for me the best advice for getting into RTAs was to try some clones. I honed my skill on things that at least made me feel like, "I didn't spend much" while I failed at using them. Full disclosure, RTAs are hard for me I have a fine motor tremor but I have made it work. Usually.
Anna