Hello mate,

For how much it would cost, I often do the same, as little as possible is best. Do you have any bits such as radio gear, that is one of the more expensive bits really, but a lot less than it used to be I am sure. Also, depends what you would like to make it from, for example wood would be cheap and fairly easy to get hold of and work with. Plastic is also fairly easy to work with but a bit more expensive then metals would start costing you more and of course the stronger the metal you use, the harder is it is work with (in general).

For the flippers part, what I would suggest is maybe doing it without the flippers then maybe add them later when you've been to a few events/got a bit more experience? Maybe then if you attend a few events you could have a talk with some of the other guys who run featherweight flippers.

Personally, I always prefer to see things working in the flesh so maybe getting a push/ram bot working and going to some events would be good? If you're not too bothered about seeing it work, there are guys on here who could help you with the pneumatics part, sadly, I am not one of them.