Would a club expect you to become licensed and fly regularly, or just to get to a solo standard? From what I've read/heard, gliding experience improves your powered flying, so I'd be happy to invest some time/money in improving my skill level. I do appreciate the tow pilot is there for the glider pilots. However, the CPL(H) is my main priority and it is expensive, so realistically there is only so much I can spend on gliding.
Majority would be happy with solo standard and not expect you to keep current. It's more to give you an appreciation of the environment you're operating in and the things a lot of powered pilots don't realise.
Things like the tow itself can be anywhere up to 80% of the cost of the flight. Flying through sinking air takes longer to get to height, and means they have to hang on longer - if you find them a thermal at 700' a lot of the switched ones will get off then (it might take them 5mins to get to 2500' as the thermal is weaker down lower, but it means they only pay for you to do a low level circuit not a climb to 3000' and back). Gliders are hard to spot, but if you have some appreciation of what marks a thermal, you're more likely to know "where" to look for them. They like going in circles a lot more than powered pilots who tend to stick with straight and level. etc. Some powered pilots take to it like a duck to water, others take a lot longer to cotton on to what's going on. Those that have reached solo standard in the gliders tend to understand all the concepts and be able to put them in to practice.