I have a tablet that has little memory and I needed an sd card so I got one, but I still have 29 GB on the sd card and when I try to download an app it says insufficient memory because I ran out of room on my internal storage
Hey do you have selected your default write disk to your sd card in settings? If not go to settings>storage and select sd card in menu. Have you got root? If you have root, then you can move every application to sd card. Try titanium backup. And if you are on android 4.0+ then you cant just move all applications to sd card. Some apps are suggested to keep in internal storage for working correctly. Just download app2sd and move the movable apps to SD card.
I had already provided you an answer but I think that you are not satisfied with it because it was for the rooted android. Now, I want to say that you can also move some apps(not all) to SD card using some app moving applications like app2sd, du speed booster etc. These are some simple applications which simply transfers the movable applications to SD card(only movable). You can also do it in settings but in these applications, you can do them together. If you want to move all applications, there is not any way to do that because without rooting, only your movable apps can be moved. If any other problem, just comment it.