Just a note - if you ever buy non-FS 510 batteries or chargers, label them and keep them separate. The FS510 is reverse electrical polarity for the batteries and chargers. So you cannot use them in any charger or PCC except FS510 ones. A more standard 510 charging cable will fry and destroy an FS510 battery and vice versa. But atomizers and cartomizers don't care about polarity.
Cartridges aka carts - you can use these a LONG time. You can add juice. When the stuffing gets bad tasting you can take the stuffing out and try to rinse it and dry it and refluff it. The empty cart can be rinsed, shook out, dried with a Qtip. Then put the stuffing back in. Or many people prefer blue foam stuffing - you can buy precut blue foam stuffing for 510 carts at strictlyejuice.com (under $1 for 10 pieces!). On a full fill you pull the foam, fill the juice cup 1/2 way (or 2/3 if you are more willing to risk the cart dumping juice out), insert the tapered end of the foam int the juice cup first and press it down into the juice to wet the foam (use an unbent smooth paper clip), reposition the foam at the top edge of the juice cup. Then top it off with a few drops of juice - whatever it needs to look just damp, not a puddle. The foam keeps it shape, very easy to rise well and pat totally dry with paper towel, wicks more consistently, less likely to give burnt stuffing taste.
Atomizers often come with nasty tasting primer on them - *blow out the atty into a tissue, drip 3 drops on the bridge /\, let that soak in, vape mostly off without inhaling.. repeat from *... Then reprime with juice (2-3 drops) and see if it is OK.
Atomizers periodically need cleaning. And if juice spills into an atomizer it may gurgle or not heat well - take it off, blow it out, clean up any wetness the the battery connections (both sides). If you bought auto batteries then you need to be extra careful to avoid leaks. Auto batteries can be damaged or killed if a small amount of juice gets in the hole in the middle of the threaded end of the battery.
After you are used to atomizer and cart, check out Boge 510 standard resistance cartomizers (slim batteries cannot use the hotter LR ones). Boge cartomizers are the most popular cartomizers on 510. More people vape with cartomizers for their favorite juices.