Homemade Dog Foods

So my brothers had two female gerbils for over a year and i had no idea how they were getting treated. They got food, water and cleaned out but no playing with or training. Ive took them into my room now and our looking after them but they arnt well behaved my questions are:
-How can i stop them biting?
-How can i get them to come to me when theyre in there cage?
-Homemade toys or treats they’d like?

Is there any health conditions gerbils get? I should know about.
Before you say I’m a bad owner-Im not. I have a dog and a small animal already so taking the gerbils on has been kinda hard. Ive got theyre food, cleaning routine and i play with them alot and have bought them a wheel and a house. But i want them to be happy because my brother rejected them and they havnt got much longer to live.