For refilling, do a google search for Taryn spin too, an easy method to speed up filling.
In general terms, there are many ways to fill a carto, but what I do is simply fill with liquid one of those protective sleeves, or condoms, which many cartomizers come with.
Then, you slowly insert the cartomizer thread first into the sleeve, slowly. You should see the juice coming up and soaking the filling (assuming you took away the top cap with a pin or a screwdriver.
This might take more than a filled condoms to achieve, as some cartos take more juice than others.
Once you see that the filler is soaked, let it rest inside the condom in for a few minutes, take it off, wipe. If there is still some left in the condom, you can drip it on the filling. Then put back the cap.
Let it rest a while, even overnight, before use, the liquid needs time to soak the filler and the atomizer as well. Taste and vapour should be better this way.
That's how I started refilling my E-lite cartos, more or less at the stage you are now, I guess.
One cheap and tiny VP which will take 510 cartos (by far the most common) is the SD keyring. It can be had for £15 or less with two cartos and charger. I like the marlboro taste.
If in the same order you get 5-10 boge empty cartos and a few bottles of liquid, you are all set for a few weeks or more of vaping on the cheap

SD prefilled cartos are also not that expensive, at around £6 for 5.
vapeescape.co.uk and other stock them.
But the cheapest option is really to buy empty cartos and liquid.
If fillign cartos is too cumbersome for you. You can get ego stardust or the new V2.
With this you just need unscrewing and pouring the liquid in. put them upside down and let rest 2 min to soak, otherwise they will taste bad, and you are ready to vape.
If you take V2 or stardust, you'll need an adapter for normal 510 connections.
The best one (as in, the only one I would recommend getting) is this long one:
510 Extension/Charging Adapter | vapourtopia
That's the only one I tried which gives a good airflow on vision stardust. I use it on ego batteries too, which in theory wouldn't need it, but it makes for a better vape.