I’d say ‘from’ is nicer, rather than ‘on’.
The on sounds like a shortened ‘on top of’ which sounds awkward.
The ‘from’ indicates that the new money will be earnt from your existing money, than a new income.
‘Earn interest from your money’ is the clearest to me. I’m going to be receiving interest and that is from my money.
However the next line explaining has interest on your ‘savings’ rather than the word ‘money’ which is also an issue. Money can be any purpose.
I don’t think the word interest needs to be dumbed down.