8 inch gecko? I'd say you could just get a 20 gallon aquarium. The live plants thing is definitely do-able. You need to put a good amount of work into that though. Fake plants are way easier.
If you wanna put live plants in, you need to buy
sterile soil or at least soil with no pesticides or toxic things in it. If you get it from the yard you just have to make sure you know where it's coming from. If you're not sure, just bake it in the oven in a thing of tinfoil for a half hour. (425-450 degrees should do it) That can be a pain if you have a lot of soil though.
You have to look up what types of plants you can put in the cage. Some plants are toxic to reptiles. Take it out of the soil it came in, rinse the roots and get rid of all the soil it was in especially if you get it from a store, you're going to have to rinse it repeatedly for a couple weeks to make sure you get all the pesticides out. (once every few days for 2 weeks)
Bedding depends on what you have, look up "marbled gecko care sheet"
Read like 5, don't just use one, everyone posts different info and it's not neccesarily correct. If you have soil down because of plants you might be able to put mulch over it or something. I haven't tried keeping plants yet. If it all seems like too much just plant one in a pot of sterile soil, you can remove it easily for cleaning.
Heat source: I personally like Ceramic heat emitters. They're a bit pricier than regular bulbs but they'll last like 5 years. (says the packaging at least, I haven't had one that long yet) If your pets nocturnal you won't really need a light source but it couldn't hurt at all. If you're pet doesn't like bright light, it'll get used to it, and it could help it regulate when it sleeps. (light comes on it thinks it's day and goes to hide and sleep) You'll definitely want a good thermostat. Either buy a couple of the analog ones or just get one digital one. Place the heat source on one side of the cage so if it gets too hot or it wants to cool off, it can go to the cool side of the cage.
Humidity you do the same thing, buy a gauge. They'll be right next to the thermometers, sometimes they're packaged together.
You get a misting bottle for increasing humidity and keep in mind heat lights kill humidity. That's why I use a heat emitter.
Eating depends on the gecko. I saw you used to catch crickets to put in though. I used to do the same thing but I guess it can be pretty bad for them. They could have parasites or something or just be moldy from being in damp crappy places that crickets tend to hang out. Buy something to keep crickets in, and though it's annoying you have to take care of crickets AND the gecko, you'll have to feed them too. You can breed them easily if you want to also. Specific care sheets for the gecko will help a lot cause it's different for each gecko. water also depends on the gecko, some will drink off the walls when you mist it, some will drink from a water dish. If you use a water dish change it everyday or 2. If you ever see it sitting in it's water dish, then change it everyday cause it probably just peed in it lmao.
Cleaning , there's usually a reptile safe cleaning spray at the pet store. This is good for spot cleaning. Clean the tank once every week or 2 this way (just wiping down the walls and w/e) Unless you see something noticeably bad, just clean it right then. I do a full cleaning and bedding replacement every 4 months. Using a small amount of bleach, if you do that then make sure you rinse it really well and let it air out. There's this stuff called virosan on the
pro exotics website, look that stuff up, I might replace all my cleaning products with that. It sounds really good I just haven't used it yet.