I usually go with 4 teams of 3 or 3 teams of 4 so it really depend of the amount of available soldier... But I usually go with 4 robots and 8 humans. The 4 robots are because at the very beginning they are really superior to humans and can soak up damage well so I ideally want one per team. It's usually the crazy soldier who cover his teamates while they flee and I often use robots in situations where a walking bomb can't be avoided. Robots have a lot of health and usually survive a walking bomb hit while normal human squaddies can easily die at the beginning because they don't have enough health (yet).
When the flying Marsec armor get available then the whole setup change. I buy 3 Marsec elerium guns and 3 psy guns along with a set of 3 Marsec armor (the red one) and fit a Mutant squad of 3 as my last (fourth) team. Mutants have nice Psy powers but are really defficient when it comes to physical training so having them kill easy targets from a distance (after I used their Psy powers) usually bring aim and endurance up to an acceptable level after several missions. The real reason why I outfit them with the Marsec armor is because they can fly with it and it weight almost nothing. If I were to equip normal armour to rookie Mutants they would have trouble walking instead of running like the others, being able to fly counter this. If I could I guess I would only equip the Marsec torso armor so they fly but the weight of the normal armor really makes a difference so I usually end up giving them full suits. Also it doesn't make much difference once you get the personnal shield technology.
For the guns I usually try to take a balanced loadout of small guns and big guns. I never take rocket launcher and I never did in any Xcom game either. I never even considered once to take those clumsy and inneficient weapons, I always wondered why others would. Probably because they are "cool". Anyways, back to the point: at the beginning I give weapons to squaddies depending of their attributes. If I spot a squaddie with high strenght and aim then I give him a big gun. If he only have high aim then he gets a sniper riffle. If they are lacking aim then I give them the minigun (the gun which fire red bullets really fast) so they can take care of the Brainsuckers on close range and gain aim points this way. And it works, I often get guys who used a minigun since the beginning to take a sniper rifle once they get veteran. Then there is usually lots of rookies to take the minigun for him anyways.
Also I
always equip my squaddies with a medpack and a grenade. Then it depend if they can take more weight without hurting their speed too much. If they can take more then I add a stun grenade, then a second grenade and then a second stun grenade. I also always place them in the shoulders, the stun grenades to the right and the normal grenades to the left, but that's just me. I do know that it was less costly in Xcom 1 and 2 in TU to take something from the shoulders than from the belt but I don't think it actually change something for Apocalypse if you play real time...
The grenade is essential because it's the last trench of defense for a squaddie if he is getting brainsucked and without anybody to help him around. Poping a grenade with the timer at 0 and immediatly dropping it to the squaddie feet will probably injure the squaddie but the Brainsucker will die from the explosion. I prefer an injured squaddie to a new ennemy in any rate.