Happy to help! I love the
underdogs allies, so want to help others
explore them if I can.
Bone saw and
stoneforge masterwork were popular when allies were in standard, but I'm sure for casual, there are some better ones out there. I haven't played them much outside of that. I'd have to look.
bonesplitter? I'm sure there are other decks here or google for that one. The other equipment played then really wasn't very good, but a lot of the ally cards have abilities that boosted equipped creatures, so you wanted 1 and zero cost equipment to let them get the synergy from that. You weren't trying to be like a bogle/enchantment deck where the things you attach make 1 creature a giant beater.
Sigarda's aid is a great way to cheat them out. It'll be fun as-is to play without going all-in on the equipment strategy. So try it out and see if you like it first.
Allies can get pretty broken if you go multi color. If you go red, you get
reckless bushwhacker (one of my all time favorite cards) and
akoum battlesinger for team pumping. If you go black, you get
zulaport cutthroat,
drana, liberator of malakir,
drana's emissary (great life gain synergy with ondu and cutthroat) and
bojuka brigand. Green has ramp and several big threats (I didn't play them at the time, since they were relatively expensive when they were standard legal) It might not have been the most consistent (b/c I'm too cheap for an expensive mana base) but my Mardu one (B/R/W) was the most fun and competitive.
Lot's of choices there!
I tried for a long time to make one that was well-rounded and competitive in Modern like elves or goblins, but they just were never quite as good. (I played 4-5 different decks dozens of times each on MTGO) They were pretty consistent, explosive, easy to learn and play, tons of fun and good enough to really win lots of games, but probably aren't going to
take down a tournament anywhere. I play 8 whack goblins and have played against a lot of elves, and both of those can win consistently on turn 4 (maybe sooner with the right draw) as to where allies are going to drag it out a turn or two longer and in Modern, most decks can stabilize or beat you by then (or they'll have mana to counter/wipe/remove everything you do.)
My suggestion to go multicolor isn't to say you should do that vs. your white deck. Just letting you know the others exist. Your white deck has several things going on... guys that grow, guys that gain you life, guys that pump the team, etc. If you like any of those in particular, pretty much each color has an ally that does that one thing, so if you want more of a particular synergy, you can really focus your deck on that play mechanic by adding more colors and focusing your strategy.
They really are an under-rated tribe and you'll have a lot of fun with it though!