Tarantulas are awesome pets!
I use Tarantula Cribs enclosures. They’re a bit on the pricey side, but they’re excellent quality and are extremely well-designed. Very secure, very easy to use, and they’re crystal clear and allow you to easily observe your spider. That said, there’s nothing wrong with doing something cheap and DYI. Any container with the right size and dimensions can just have some ventilation added and voila, spider enclosure! Though one caveat with DYI enclosures: remember that tarantulas are surprisingly strong for their size. They can push up lids that are not secure. And slings are very small and can escape through very small holes and gaps. I’d also avoid using anything with a mesh lid or mesh ventilation, as tarantulas can get their little toe claws stuck in it, and they can also chew through wire mesh and potentially escape.
I feed my spiders a variety of feeder insects. Mainly crickets, dubia roaches, and mealworms, though I’ll occasionally get hornworms, and sometimes get super worms for my bigger gals. For very tiny slings that are too small to take pinhead crickets, I’ll usually just prekill a small cricket or mealworm and leave it at the mouth of their den. Slings will scavenge, so I find that easier than dealing with fruit flies.
Feeding frequency depends on age, and on the size of the meal. I also tend to feed my spiders less often than most care guided recommend (I just feel like we tend to feed animals like snakes and spiders too much in captivity). I go more based on the size of their abdomen than a set schedule. When they start looking a little less plump, I’ll feed them. For small slings, that usually ends up being once, maybe twice a week. For juveniles, maybe once every 10 days. For older juveniles and adults, maybe once every two weeks or so. But those time-frames are just ballpark estimates, actual frequency may be more or less depending on how quickly they seem to be burning through their last meal.
They typically won’t eat when they’re in premolt, so be prepared for that. Don’t feed them right after a molt, wait a week or so for their new exoskeleton to harden (can take several weeks for larger Ts). Feeders can actually injure or kill a freshly molted tarantula, so just make sure to always remove any feeders that don’t get eaten.
If you have a species that needs humidity, I recommend adding water to the substrate rather than misting. I’ll make little holes in the substrate in the corners of the enclosure and drip water down those holes with a pipet. This adds humidity while also creating a more natural moisture gradient and avoiding things getting too wet and soupy. The top of the substrate stays dry, but the lower layers are damp.
I do recommend giving your spider a water dish. Not everyone does, but I do see mine drink from their dishes with some frequency, so I recommend water dishes. You can just use something like a small bottle cap in small enclosures.
Sorry for the info dump. Happy to answer any more specific questions.