You will still need food, conditioner, and a filter. Plants will feed on the ammonia and nitrites produced by your fish and its waste, so they do help the water quality. Heavily planted tanks can get by with fewer water changes and/or less water changed each time. But most people just getting into plants aren't going to jump right into a heavily planted setup, so a few plants will probably not allow you to alter your maintenance routine; however, they do help keep the aquarium stable and healthy between changes. Plants also provide a more natural environment for fish, helping them feel more secure and comfortable in their surroundings. And you don't have to worry about them damaging fins like you do with fake plants.
Some fish eat plants, which can be both good (source of food for fish) and bad (if you want your plants to actually thrive). Bettas, however, will not eat plants because they are carnivores, so this is a nonissue if bettas are the only fish you keep.
Some plants, such as marimo balls, can help keep certain types of algae at bay.
There are some drawbacks to live plants. If, for whatever reason, your plants do not flourish and/or you are not careful to trim dead leaves, decaying plant matter can hurt your water chemistry. So you need to check your plants regularly to ensure that they are healthy and don't need pruning. This in itself adds a little more work to the fishkeeper's routine.
Different plants have different needs as far as lighting, water chemistry, and fertilizers, so you need to research each species that you are considering adding to make sure that the plant is right for your setup. If you want medium--high light plants, you will need to invest in a lighting system that is much better than the standard lights that come with most hoods. Some plants need fertilizer and CO2 to thrive, so that can be an added cost. But there are many plants out there that are perfectly suited to low light tanks without fertilizers, so this shouldn't discourage you; it's just something you'll need to keep in mind when thinking about what kinds of plants to get. Some plants get too large for smaller tanks and/or grow so quickly that they can overwhelm a tank; the size and growth rate is another thing you'll need to consider when researching types of plants.
Another potential drawback to plants is that, if they are not treated (e.g., with bleach or an anti-snail treatment) or quarantined, they can introduce hitchhikers, like invasive snails, or even disease (if they were kept in a tank with fish at the pet store/fish store) to your tank. But treating/quarantining plants before adding them to the tank can mitigate this issue. Sometimes planted tanks can be prone to algae because you will need to leave the light on in the tank for a good part of the day; if you get plants that need fertilizer, algae also loves ferts. But a low-light setup without ferts shouldn't be too bad in the algae department, and, as mentioned above, some plants (like marimo) can help prevent algae.
Some good beginner plants with low lighting needs and that don't require fertilizers or special equipment include:
most anubias species
java ferns
ancharis
most crypts
marimo balls
dwarf water lettuce
banana plants
windelov