If you're thinking of breeding shrimp then a dedicated shrimp tank is really a must.
Have a look on Planteinvert.com - there's loads of information about shrimp and their requirements which in some cases are quite exacting and others have quite a wide range of tolerance for things like pH, TDS, temperature, nitrate levels etc. Just make sure you can readily provide what they need before you buy. It would be a huge shame to lose shrimp no matter how inexpensive they are because of lack of adequate preparation.
If you want to go the betta route - try the larger shrimp like amano/yamato as they are big enough to ping out of the way if the betta isn't too friendly. The cherry types don't tend to do well with bettas in my experience.