Hi, kit-kat, and welcome!
I think you get the things confused a bit, exactly like I did when I first started this.
First of all, 510, 901 and 808 are really just designations for the type of connection / threads. They don't say much about the device itself - atomizer, cartomizer. While there may be some truth to the fact that certain people prefer the draw on 901 atomizers, the cartomizers are fairly identical across connection types. There are different types of cartomizers, but they differ in the way they are built, regardless of connection type. You are right, however, that the 510 connection is the most popular and a higher number of different vaping attachments come with that connection type.
If what you are looking for is direct dripping using an atomizer (this is great for excellent flavor, less great for portability and requires a bit of a learning curve) - then you will need a new setup altogether. And it should probably be a 510 threaded device.
But I really think you shouldn't discount cartomizers for good.
I am assuming you are using pre-filled cartomizers, right? Well, for one thing, you can re-fill pretty much any cartomizer (regardless of it being 510, 901 or 808) and you can find blank 808 cartos as well...
I am assuming, again, that you have a slim / cigarette lookalike automatic battery - in which case your options are further limited by the fact that such battery cannot power some of the cartomizers out there, and also you won't be able to enjoy, say, direct dripping because any juice getting into your battery would ruin it. In fact, much of your problem seems to be due to (1) poorly filled cartomizers and (2) a poor quality automatic battery -- if that's the case, refilling your own cartomizers and using a manual, better quality battery, should solve it.
If you are determined to stay with a slim battery setup, look into the 808D-1 such as the offerings of Vapor4Life or, even more popular around here, SmokelessImage. If not, then start thinking about an Ego-style battery that'll give you the best entry level choice in terms of flexibility. Egos are 510, but with an adapter you can connect anything to them anyway.
Again, I'm not sure what you are looking for - give more details if you want, and people here will be sure to help.