So I wrote this up for a friend that's first getting into the game, and I figured I'd share it here. I tried as much as possible to put things in a way that's easily translatable to a COH player. From here, you can find more detailed info on the CO forums. I can also try to field some questions, but keep in mind that I've been playing for less than three months.
For your primary superstat, I recommend Constitution. You get two secondaries as you level- I would definitely make Intelligence the second one, and if you're playing ranged, either Ego or Dexterity as the third.
For your power selections, here's what every character should have.
1.) An energy builder. Self explanatory.
2.) A single target attack. Self explanatory.
3.) A slotted passive. You can only have one active at a time. This is basically the equivalent of all your toggles in a COH build. I recommend Invulnerability from the Power Armor framework as your passive, but here's a full list:
http://www.champions-online-wiki.com/wiki/Slotted_Passive4.) An AOE attack. Self explanatory.
5.) A self heal. The best one in my opinion is Conviction from the Celestial framework, or Bountiful Chi Resurgence if you use Masterful Dodge (I'll get to that.) Here's a full list:
http://www.champions-online-wiki.com/wiki/Healing6.) An active defense. These are basically like "Moment of Glory" powers. They also work like break free's if you get mezzed. The best one in my opinion is Masterful Dodge. Here's a full list:
http://www.champions-online-wiki.com/wiki/Active_Defense7.) A toggle power. You can only have one active at a time. Pick which one you get based on your super stats. If you're going full ranged, I recommend Concentration. Here's a full list:
http://www.champions-online-wiki.com/wiki/Form8.) An active offense. These are like "aim," build up, Rage, etc. Either go with two active defenses or two active offenses, depending on if you'd rather do more DPS or be more durable. For range, and if you go super DEX especially, I recommend Ego Surge and Lock n' Load. Here's a full list:
http://www.champions-online-wiki.com/wiki/Active_Offense9.) An energy unlock. These are powers that return energy to you under certain conditions. If you build right, you'll get to a point where you never have to use your energy builder. The best energy unlock in my opinion is Molecular Self Assembly from Technology. Here's a full list:
http://www.champions-online-wiki.com/wiki/Energy_Unlock10.) Something to feed Molecular Self Assembly. This power grants you energy every time a power comes off cooldown, so it's good to have a really short cooldown power or two. You can browse the wiki for short cooldown powers, but on a full ranged build I recommend taking Evasive Maneuvers from Archery, especially if you take Masterful Dodge as your active defense.
11.) A block upgrade. These are different ways to make your block much more powerful and add different perks to it. If you use Evasive Maneuvers and Masterful Dodge, I definitely recommend Parry with the Elusive Monk advantage. Here's a full list:
http://www.champions-online-wiki.com/wiki/BlockFor the rest of your powers, there's really quite a bit of flexibility. These essentials or some variation should be taken on all builds though.
As for your gear, do the quest lines, and you'll get gear as rewards and drops from mobs. Equip gear based on your super stats- So if you're super Constitution, equip constitution gear. You'll find gear that includes all of your super stats as you level more and more, but focus on what you have at the time.
Same deal with talents, base which talents you pick around your super stats. Once you get to level 10, you'll unlock specializations. Your first specialization will be your primary super stat. Always upgrade gear enhancing specializations to max.
Once you get 10 points in that tree, you unlock your second specialization tree. I highly recommend picking vindicator, and slotting the Rush of Battle to max immediately. This provides a self heal over time whenever you defeat an enemy, and it's awesome to level with.