There is already a mistake in the question. Asking “what is the currency I need?” is like asking “do I need a screwdriver or a hammer to build my house?”. You need both, and many other tools. This is the same with currencies. Every community will need an appropriate set of different currencies that will work together in a systemic way. You will certainly need at least a currency to trade (buy/sell), maybe some currencies to measure (performance, number of transactions, energy, carbon emission, etc), and some currencies to acknowledge (someone’s expertise, someone’s level of trust given by the community(ie. eBay), someone’s coolness, and so on.)
If you decide to create a mutual credit currency for trading, you may want to link it with someone’s reputation in the community to establish credit limits. The more trust this person has gained, the more he/she can go positive or negative.
As you see, we are moving from the stone age — one currency for everything — to the era of multi-currencies that, finally, express social life in a much more evolved way!