As far as atomizer cartridges go - not likely you will need more than 5 ever. Cartridges are just not a great way to vape. And they can be restuffed and reused for a long time (if they are standard 510 carts, strictlyejuice sells precut blue foam stuffing). I use a drip tip for testing juices and vaping juices that didn't earn cartos or juices that are thicker than i will put in cartos. Cartridges may make sense while you try to find juices you really like. My main favorite vapes which are thin fairly clear light juices (so they don't drop carto-clogging flavoring sediment) go in cartomizers.
This is how I fill cartos. After you do it once it will be easy.
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How I fill Vapor4Life KR8 cartos and Boge 510 cartos
Pop out the soft cap with an unbent paperclip in the mouth hole, very careful not to catch stuffing or the wire loop.
Shake and open the eliquid
Hold a bit of tissue on the threaded end hole, tilt the carto, and add 18 drops per ml of capacity into the stuffing (Boges and most KR8 cartos are about 1ml).
Wait 15 seconds or so then see how many more drops the carto stuffing will soak in easily.
Clean up the threaded end, tilt open end down into tissue, puff into threaded end to clear air channel (Boges and the KR8 cartos I use have a defined center air channel and I want to see light through that)
Sop up any loose juice above the stuffing
Cap and let it settle - I lay it on different sides for 15-20 minutes to make sure every bit of stuffing gets damp so I won't singe the carto. if you use thicker juice than me (I use 20% Vg or less) then you may need to wait much longer.
While vaping, if the vapor gets a bit light or a bit dry or the carto is getting hotter than normal, I take the carto off the battery and add eliquid. I sometimes use a plastic or delrin drip tip as a mouthpiece on Boge and KR8 cartos (not to drip into since the juice would head for the central air channel)