Renting points, while cheaper than booking DVC villas direct via disney, is great, but in demand properties and villas types go fast. Negatives of DVC rentals, dates are not flexible and villa options at various resorts are limited for non- DVC owners. When you search DVC rental availability, it's really not an accurate picture of what's really available given DVC villa availability is constantly changing.
You're best bet is to get with a reputable DVC agency and let them know what you're looking for and when and see what they have. The more date and location flexible you are, the better off you'll be for renting points.
Also, keep in mind, your options for cancellations/changes will be much more limiting than that of booking directly with WDW so that may be a concern given you have such a large group. A group of friends may have last min cancellations/changes and people may bail and leave you or others in the group with a hefty hotel room expense with less flexibility to change your reservations. Be sure if you do rent points that ya'll understand the nature of cancellations/changes and fees.
As far as when to go given you all can travel most anytime, pick value seasons and see what your group thinks. There are pros/cons to visiting these times of year which is usually lower crowds but can have some drawbacks. Like September, great low crowd time of year, but super duper rainy, still hot and tropical depressions are a factor; January, also low crowd but can be really cold. I'd poll your group and get a season in mind and see what the DVC agency can find.
If it's me and I can travel anytime, I'd pick late February/early March and mid Nov. It's not necessarily low crowd or value season for any of these times of year, but it's milder temps which makes trips very enjoyable and typically not rainy. I really like mid November, again not low crowds but it's after Jersey week, before thanksgiving and you get a taste of Xmas and milder temps.
As far as where to stay, a group of 20 something single folks, maybe BWV- great location to Ep/DHS and lots of dining/lounge options all nearby. If you are really wanting the most space, OKW has some large villas but not my favorite location but would be more budget friendly. SSR also will be more budget friendly than the BW area villas.
If you decide against renting points, our favorite more budget friendly resorts are POFQ, Swan/Dolphin and GDT at CSR.