Understand the need to conserve money, however...

Consider your needs (as I don't know them) and get a good tablet if the sensitivity and tilt- stylos
attributes are important. If you're painting textures, I would say that it is worth saving up for a good tablet rather than making do with a cheaper one. 

I've got an Intuos-1 6x8 that is still a good tablet after 10 years

and a Intuos 4 ptk-840 (which is around 8.5"  X  13"

I've never used a Bamboo so I have no feedback.

Most important part: 

Don't minimize the feel of the pen. If you're going to be spending hours holding it be sure to get a good grip. Even pinching hurts when you do it for days and days. ; )