Easy, get yourself a good guidebook and a few 7 day bus passes and go and visit stuff that is free, alternatively don't even buy a guidebook but go to the Tourist info office at Luqa Airport or indeed at City Gate Valletta and pick up a mountain of free leaflets and brochures and maps about village walks, city / history walks such Birgu and Valletta and leaflets about churches and gardens in Malta they are all free to do, we have done loads of these walks and they are ace, and by using the bus you will have an almost free day out, ask again if you want me to tell you a few free / dead cheap things and I will happilly do so but in my own time.
Regards
Sliema2