I only use cotton bacon prime - it is very easy to not use enough cotton, if the wick slides through the cotton without pulling at the coil it will spit and gurgle like crazy because the cotton is too loosely held inside the coil.
Generally MTL coils are wrapped from thin wire and it doesn't take much to drag them out of position when wicking. Try using more cotton than you have previously, Twist the end of the wick to a HARD point (don't be scared of twisting the crap out of it as this bit of cotton will be cut away and discarded), feed it through the coil and pull it through (you may have to hold the coil in position with your thumbnail to stop the cotton dragging the coil out of position). If the cotton slides through easily YOU HAVEN'T USED ENOUGH, If there is too much cotton it will bunch up and you will have to use force to pull it through which means YOU HAVE USED TOO MUCH ( in this case just back the cotton out a little, pinch a tiny sliver of the cotton between your finger and thumb and peel it away to thin the cotton slightly - it helps if you gently twist the remainder of the cotton you are trying to pull through the coils and smooth it with your fingers. Then try to feed this slightly thinner length of wick through the coil.
What I think you are missing is the knowledge of how much resistance you need to FEEL when putting cotton through a coil. Too little and it slides through too easily, too much and it will drag the coil out of position and totally distort it. You need to be somewhere in the middle where the cotton is held fairly firmly inside the coil, but not so firm the cotton is compressed so tightly juice cannot travel through the fibres (which will give dry hits and burnt cotton).
Unfortunately how much resistance you should feel cannot be learned from Youtube build instruction vids or looking a photographs of other people's builds,. The cotton shouldn't slide through without resistance, it also shouldn't have to be forced through, you should just feel some resistance - but how much is some? Enough to pull the coil - but not drag it. What??
I recommend you try again using a little more cotton, if you get frustrated just put it to one side and come back to it when you're less wound up. Learning how to wick any RTA is a frustrating experience and knowing how tightly to wick and how much cotton to use in the juice ports catches pretty much everyone out at first, but when it clicks into place it's kind of like learning how to ride a bike.
Personally I don't think you should sell it, if you buy a different RTA you will probably still have the same issue and if you give up totally you will be stuck with stock coils/pods forever. For the moment vape whatever you're currently using and just have a go at wicking the damn thing occasionally when you have a spare half hour, if you screw up don't get wound up or worry too much, just put it away and come back to it later - almost everybody goes through the same stage with RTAs