You don't say what your budget is, but here are a few suggestions:
A small make-up bag each with a couple of items such as nail polish, lipstick (if you know the colours they'd each prefer), nail files (cost would vary depending on what you choose)
Bath bombs from Lush (around €5 each)
Photo frame - Easons, Arnotts and Past Times do lovely ranges that aren't all that expensive (if you have a group photo of all the friends you could maybe pop that in too)
An accessory of some sort chosen for each individual (such as a really nice hairslide or scrunchy for those with long hair, some inexpensive earrings, a scarf)
An idea for gift-wrapping that I find cheap but effective (makes even the cheapest gift look special!) is to buy some sheets of plastic tissue wrap (M&S sometimes do it, Clerys and Easons generally have it) and tissue paper. Lay a sheet of tissue paper on top of the sheet of plastic, place the gift in the middle, scrunch the wrap around it, and tie it with gift ribbon. This could also cut costs on the make-up bag idea, if you just wrap the items like this instead.
Hope some of these ideas help.
Lastly, glad to hear that you had your friends around you during that bad patch - where would we be without them?