Id recommend you build featherweights first.

Firstly, if its a club you would want several robots to play around with. Having just one heavy limits what you could do as a club, and also would limit how much work you could do it on it outside event time. If you bought 3 feathers you could play with each other in the meantime, and work to perfect your designs.

Secondly, heavies dont come on the market very often. And many which are currently available to buy may require extensive modernisation. Feathers are easy to build with help, and you can get others to build for you if your really worried (then look at how they done it and copy)

Also, avoid building a heavyweight at all costs.