You can use the bottles the vodka comes in (just empty a small amount out so you can put stuff in). You could give them as presents on the original bottle or get Kilner type bottles (500ml or 250ml) from amazon/eBay & other places & Lakeland do a 6 pack of presentation bottles (100ml bottles) which are a great size if you're making a few flavours to give the same person.
As for flavours, there's loads if you search for recipes. You can add sweets like skittles, black jacks, cola cubes, werthers toffees, mints, most hard sweets will work. Just shove them in the bottle of vodka & keep shaking for week or so. Some sweets form a scum on the top of the vodka so you'll need to filter into another bottle to give as presents. Just get a coffee filter (or muslin or piece of kitchen roll in a sieve) & filter til all the scum has gone.
For more natural fruit flavours, you just add the fruit (eg cranberries - prick each cranberry first to release flavour), plums, berries, add to vodka with sugar (you'll need to find recipe to get quantities) & keep shaking every day. If you want to make fruit ones for Christmas, you might have to start soon so the flavours can develop whereas the sweet ones don't need as much time.
You could even make a chilli flavoured or limoncello.
Have fun 