Typically the waste valve diameter is about twice that of the drive pipe bore. This can vary a lot with type of valve.

For a given water flow there is an optimum drive pipe size but you have a fair latitude. If you have no limit to the water available then a larger than normal drive pipe would let you increase water pumped at a later stage if you wanted but don't go wide of the normal marks.

Google hydraulic ram and you will find lots of data. Try Green & carter and Blake websites and they will give ram sizes and drive pipe sizes with delivery in gallons per day.

Some will specify drive pipe lengths for a given head. These figures vary wildly and seem based on ancient myth. My own findings are that long drive pipes only slow the operation and that may suit certain types of valve. Even vertical drive pipes work ok with the correct valve. If you have to have a very long pipe to get the head it still works but anything greater than 10 times the head is better avoided.In this case it is better to bring the water horizontally ( or virtually so) in a large pipe or channel and then drop to the ram from a feed tank with a pipe slope of about 1 in 4.

Delivery valve type also has some effect on operation but is far less critical than the waste valve.If you don't keep the air in the air vessel contained within a flexible rubber tube or diaphragm then in most water areas you will need a snifting valve to keep the air vessel topped up. A few water supplies are sufficiently aerated not to need this but that is not usual. Put a wheelbarrow tube or similar in the air vessel and not mess with snifters is my advice.