ya amano shrimp are easy... they do get bigger than cherry shrimp though so couldnt have as many, also as far as a centerpiece fish just make sure that no fish in that tanks MOUTH is big enough to eat the shrimp because if it is, they will be expensive treats...
I have some suggestions as the Shrimp go... The ghost shrimp is usually your cheapest can go from 25 cents apiece up to 3 dollars apeice some places, but they usually arent kept in great conditions because they are purchased in bulk and they do also get to around 1 to 1.5 inches
Cherry shrimp are great, they stay smaller than 1 inch, the females get red and the males are kinda Pinkish, they cost from around 2.50 to 5 dollars apiece
tiger shrimp look like ghost shrimp but they have black lines on there back, from my experience they are a little tougher to keep and are around 3-5 dollars
yellow shrimp, blueberry shrimp, sunkist shirmp, red crystal shrimp are some of the most eye pleasing shrimp you can get, but most of them can range from 5 to 12 dollars apiece and are not something i would suggest to a beginner since the cost is high
I would like to mention my favorite type of shrimp and there is some debate as to if they are a differe species or not
Sakura Shrimp which basically look like VERY red cherry shrimp, they stay about the same size but are much more colorful, some will say they are just hand picked cherry shrimp but I believe they are a different species and they can go from about 4-6 dollars apiece but they are pretty durable