Reliable allies are active friends who can give you at max 50 U-ISO8s during SpecOps (Energy or other giftable items outside the SpecOps Event duration). If you still have trouble getting the max 50 daily allowable accept-resend U-ISO8s, find/request more friends. Take note that some new friends would sometimes be only available for ally recruitment 2-7 days after you've accepted them as Facebook friends, so it is recommendable to do recruitment before a SpecOps starts!
Dummy Accounts are used by some players, a cheat if you may, that enables a player to compensate the lack/absence/inadequency of U-ISO8s s/he is getting daily. This is only recommendable for players who can shuffle between two/more accounts (a person who has a lot of time).
By Visiting Allies, you can gather Energies, SHIELD Points, and Silver Coins. During SpecOps, you can also get U-ISO8s. It is recommended that you "farm" or visit your allies only after your energy meter bar runs below 10. And if you're aiming to 5-Star a SpecOps Mission, killing an enemy unit with a Distress Call would activate the Call in the Cavalry Bonus, which grants additional 100 points per enemy defeated through Distress Call. Distress Calls are also important for some SpecOps that require its use.
Inactive Allies are friends who tried playing the game, but has not been participating occasionally. Even so, their accounts can still help out for when you need to farm additional U-ISO8 and Energy, so don't be too quick to remove those if you have a low amount of allies.
Some enemies drop items, and during SpecOps Seasons, one of those items are U-ISO8s. So when you run out of U-ISO8s and still have a lot of time, try your luck by farming from S.H.I.E.L.D. Simulator and/or PVP (Practice and/or Tournament).
When adding someone in Facebook as a potential ally, send them a message (through Facebook Messages) indicating your intent to add them as an ally. This gesture can be seen as an act of modesty and would appear to the other side that you are sincere (even if you're not, it will look like sincere, see Inverted Tony Stark as an example). It will also give the other person an idea of why you are adding them, 'coz seriously, I (for example) has been receiving a lot of friend requests who are really adding friends just so they can tag them on some weird advertisement post (what the heck would I want a "Human-Sized Hamster Wheel" for?).