While the screen and camera are built in and rarely upgradeable, here’s what can be done to improve a cheap android tablet. Most tablets include a memory/storage expansion slot that will allow you to insert up to 32GB of storage. This will make plenty of room for additional apps or picture storage.
A cheap Android tablet will most often include wi-fi that is easily as good as, if not better than a brand name tablet. Wi-fi hardware either works or it doesn’t, there are very few occasions where it works poorly. If you find the hardware to work poorly, it cna usually be improved by updating to the manufacturer’s latest software image.