Today i had an argument with a friend who when i showed him the game, said that card effects such as City Gates, Keystone Forge are effects that happen one time, the next start of your turn and thats the only time. The rulebook states that cards that don't have a bolded trigger are constant effects. keystone forge and city gates both have a bolded "Forced". Is he right?

Depends on what he is saying. Is he saying that when you play Keystone Forge, at the start of your next turn, you heal 1 dmg from your capital, but turns after that it does nothing? If so, he is wrong. Forceds kick everytime their trigger is met, in case of the Keystone Forge, this means each time your turn begins, it triggers.

A Forced Effect is not a constant effect it is a triggered effect which the game state checks and forces into initiation regardless of player intent and it happens every single time the triggering event happens. This may be multiple times in a phase, once a phase, once a turn, or because of conditions once a game (or even never)... but as soon as the tirggering event resolves the Forced Effect will trigger itself.

Okay, I have one more question. Archmage of Saphery says

Quest. Action; During your quest phase, you may heal 1 damage on one target unit. (limit once per turn.)

Now, is this saying that i can heal 1 damage every turn on my quest phase, or is it saying that I can only heal one turn total, and that it's stating to only heal 1 unit during that 1 turn.

I guess what the problem is, is what is so hard about FFG just putting "Every turn" on some of these cards?

It says limit once per turn. Something that can only be done wouldn't say once per turn it would say when it enters play or something like that.

Do not mistake FFG not using the words you expect as being the same thing as poor wording. This effect is pretty simple to understand if you have read the rulebook. Here is the breakdown -

Archmage of Saphery

Quest. Action: During your quest phase, you may heal 1 damage on one target unit. (limit once per turn.)

"Quest." - Page 16, "Some card effects are preceded by an italicized zone name. (Kingdom, Quest, or Battlefield.) Such effects are only active when the card is located in the specified zone."

"Action:" - Page 15, "Actions are denoted by a bold “Action:” trigger on a card. Actions are always optional, and can be triggered by either player during any action window in the game sequence. In order to trigger an action on a unit, support, or quest card, the card on which the action is printed must be in play, unless the action specifies that it can be triggered from an out of play state."

The last part that you question is "(limit once per turn)," which is very plain English that says 'this effect can only be triggered once per turn.' Is there another way for you to interpret this limitation given the other parts of the card and how the rulebook tells us we should read and play them?