I'd go with Gambeson padded cloth. The maximum protection version third of the price of the cheapest metal armor (and much cheaper than full plate). A cheaper and thinner is usually worn underneath metal amours to provide padding (the metal stops blades and weapons but not the kinetic force so the cloth tries to absorb some of it... not all), but those specifically made for stand-alone are on average 12.5% thicker (it depends on the craftsman).
What can it protect against?
Longbows shots from beyond 10 meters. Yeah, longbow shots except at point blank can't even penetrate special cloth, much less full plate armor. At long range it's more likely to knock you off your horse (possibly fatal), go into the eye hole (fatal), into an armor joint hole (often incapacitating thanks to blood loss), than go through the full plate (it might make a nice dent if the angle isn't shallow... does shooting 70 shots in the same spot make the dent deep enough for a hole?). As I said, even Gambeson can protect against those arrows, look it on YouTube.
If you get within 10 meters of an archer, you probably have the edge as he isn't trained to use his melee weapon, unless you're in Japan since samurai know how to use lots of weapons.
Contemporary crossbow shots at almost any range, for the same reason. Yes, one could make a crossbow with a more powerful shot, but there must be some drawback at some limit because there is an upper limit to what was historically made.
Battle axe blades. Note that it only provides partial cushion to the force, so it turns the axe attack into an effective blunt trauma.
Sword slashes. Gambeson laughs at slashing attempts.
Pistol shots at non-right angles. Yeah, pistol shots don't do much to properly better plate mail either. With a pistol, you can only take on chainmail, scalemale, wrought-iron type armour, and the poor noble who took on a shoddy reject (they used to actually shoot bullets at early renaissance plate mail to prove the bullet proof ability of finely crafted armor, the rejects might be good against arrows) Don't want to get hit with a musket ball with any of these armor though.
All of these attacks are likely to penetrate the first layer and make a nice hole... leaving the other layers and your skin intact.
What does it not protect against? It's poor against maces (keeps the mace away from the skin, but the force goes though). Like most armor, it can't provide much protection against blunt trauma, although it's actually better than briganidinel worm without cloth underneath for that. Most armor can't really get rid of the force, only the blade. Gambeson is not good at all against any for of stabbing. Which means it's slightly better than useless against sword stabs, spears, lance charges, etc (if you're lucky the stab is slowed down from bone shattering to flesh tearing speeds).
An arrow is a stabbing motion so one might wonder why it's worse than a spear. My guess is that the arrow is lighter. If someone was going to hit you with a punch or a pistol bullet, the damage it takes depends on if it penetrates. Against skin, the pistol penetrates due to force apply to a smaller area so it hurts more. If you are wearing a flak jacket, pistol shots are too weka to go through. Both the punch and the pistol bullet would apply their force to the flak jacket, which transmits the force to you. However, the punch has more mass and if you multiply by the speeds, there is more momentum in a punch. Therefore, when the skin isn't penetrated, the punch hurts more due to the greater momentum. I'm guessing that the spear penetrates gambeson because the man behind the thrust can keep applying the force while the arrow is on its own, hence why it has to be a point blank shot to go through gambeson.
Wait, almost everyone could stab with a spear or sword. Yes, this is true.
But slashing is easier with a sword than stabbing for most two-handed swords and some one-handed ones. So you deny their easier attack that could land on you more easily.
This is still inferior to most metal armor except weight. But I mistakenly thought the OP said "protection,usefulness,flexibility, how long to fix/repair, and cost efectivness" and not
weight, protection,usefulness,flexibility, how long to fix/repair?
So... hey gambeson plus a kite shield is much cheaper than most medieval metal armor alone and marginally lighter than that armor alone. Gambeson plus a buckler might make the comparison look even better, although still inferior to brigadine and platemail. It's why gambeson plus shield was really common before practical muskets, and still somewhat common in the "guns are useful but we still need melee fighters because no one invented the bayonet yet" time.