Now I will confess I am not expert on this period and my haphazard approach will no doubt have more dedicated ancients gamers pulling out their beards but I'm giving it a go. I'm not sure what rules I'll end up using, probably WAB to start (I have v 1.0 somewhere) but am looking forward to seeing the Black Powder inspired ancients game later this year as well as others (possibly Phil Hendry's). Whatever, I am basing figures as I do for WHFB, individually and using movement trays.
I am also trying a new approach to painting by painting the least interesting/most effort/larger force first as I have identified this as a possible reason for projects remaining unfinished. Accordingly I am not starting with the interesting, uniform, small unit Romans but with the Celts.
Counting my boxes I have 186 foot, I'm not 100% sure how large my Celt warbands should be, kinda assuming 28 or 35 (ranked 7 x 4 or 7 x 5). Anyway the first effort has been to convert some into sling and javelin armed skirmishers and eight of each are now in various states of painting/dipping at present (so only another 170 to go!). Hopefully pictures in the next day or so.
To help improve my ignorance of the period I have picked up and started reading Stephen Dando-Collins' Caesar's Legion: The Epic Saga of Julius Caesar's Elite Tenth Legion, which may not be 100% accurate judging from the reviews but is eminently readable.
Celt painted running total: