Not pasta salad as suggested by previous poster - that's unlikely to be GF.
You can get GF pasta but it's not generally very nice. Other PP's suugestions sound v good, however..
Hummus (ideally home-made and without tahini) with carrot sticks and red pepper strips.
Aubergine dip and blini/buckwheat pancakes. (Both easy to make.)
Smoked salmon pate (home-made, to be sure of GF: just smoked salmon pieces and soft cheese and parsley and black pepper) and wafer-thin slices of Granny Smith apples to dip, and lemon wedges.
Vine leaves stuffed with rice and herbs.
Buckweat grain pilaf or rice similar.
Fritters based on chopped veg, spices, chopped spring onion etc and gram flour.
Ratatouille with lots of garlic and fresh parsley.
Aioli with various cold/lightlly cooked veg.
Potato salad with GF mayonnaise plus a little 'live' apple cider vinegar, plenty of chopped apple, chopped gherkins or capers, chopped spring onion, lots of fresh parsley and black pepper and a tiny twinge of fresh tarragon.
Toasted nuts, puffed salted giant corn (maize) kernels as nibbles.
Little squares of frittata - with any combination of spinach, spring onion, asparagus, fresh herbs and gated strong cheese on top.
Fried mushroom and onion frittata.
Broccoli and salmon frittata.
Vey spicy salsa with sour cream, grated cheddar and GF torilla chips.
VERY retro:
Mini-cocktail sausages on sticks (if gluten free).
Fresh pineapple and cheese cubes on cocktail sticks. Can add halved mini tomatoes if liked.
Sorry if this duplicates any previous mentions. Wrote this then had to dish up supper; have only now retured to thread.