Thats a bit difficult to say how much you should budget, all depends on your flavour profile and if you are going with the Top up kit or the full kit. Either way, which ever kit you get, you should consider taking a few extra concentrates to broaden you mixes, maybe add an additive like EM...
great stuff, if you really get stuck with a decision, then you can always count on the forum to provide answers or you can also chat with Derick and Melinda from sky blue.
Not to fortget, there are also other registered vendors on the forum such as Vapour Mountain and Valley Vapour, who also...
If want to get into DIY and have some knowledge in measuring volumes, then you should be able to mix up some nice juice :)
If the Full DIY kit is a bit expensive, you could always get their topup kit which has the necessary base PG,VG,NIC and 2 flavours which is a bit cheaper and will open up...
DIY is quite easy, unless you start getting into the complex mixes, but there are lots of useful recipes on the forum. I normally buy my juice from Vape Cartel and then DIY on the side line.
From what I checked online, the clear section is just there to help cool the vape down when building super low builds, by adding extra space in the chamber. Cant be used as an RTA