your question is a little confusing, youre looking for an all purpose wakeboard, or a kneeboard?
If u need a kneeboard any old one u can get off ebay will do the job. As for an all purpose wakeboard, just get one of the entry level ones from any of the major manufactures. For bindings if it is going to be used by multiple riders the velcro series from LF like the vantage will do a good job. For board size u probably want a middle of the road length like a 137-139 for adults or 130-134 for kids.