https://www.petsmart.com/fish/tanks...s-aquarium-starter-kit-40713.html?cgid=300207
Would this kit be worth getting for a betta in the 10 gallon size? Is it actually cheaper to get it in the kit? It seems like it, because the stuff is expensive alone. Is this a good kit with stuff I could use?
Kit: probably fine.
Filter: probably fine, but if it moves the water too fast--just put a rock, branch, or plant in front of it, and that will slow the water down.
Light: probably fine for fish, OK for low-light plants (java fern, java moss, maybe a few others), not good for most other kinds of aquarium plants.
I cannot see details about the light, I'm just going with basic idea that a kit never has a plant-specific light.
For the price I'm seeing, it's probably a fair deal.
If you try to buy the parts separately, you may end up with "better" forms of some of them, but I think you will end up spending more money. I also think the quality in the kit will be fine.
I wouldn't bother with it. Just get some pretty-colored gravel.
Some plants do not grow roots, and even the ones that do can be fine in gravel.
If you mostly want a betta, don't get complicated with the plants. Stick with simple ones (like the java fern I keep recommending).
If you really want to do an underwater garden, then you've got a lot more research to do before you buy anything. Different plants have different needs, so you have to either choose the plants and then meet their needs, or choose the conditions and then only get plants that like them.
Also be aware that algae is a plant, but one that many people do not like. You might need to regularly scrape it off the glass, so you can see into the tank, for example. You will probably have some algae no matter what you do, but the more you make conditions right for plants, the faster the algae will grow.
Algae can have its good points-- it will use fish waste just as well as other plants will (which is good for the fish), a layer of algae can make things smoother which is good for betta fins, and aquarium decorations like castles or pirate ships can look good with algae growing on them.
There are also forums for aquarium owners, and even specific ones for people growing aquatic plants--just reading through the old posts on such a forum can teach you a lot!