What does item level mean?
Item Level, or IL a more common reference in the game, specifically refers to progression level in the game. It is not a measurement which implies competence or skill, but simply a numeric value which represents the sum total of the following:
a) Guild rank, each guild has a rank from 1 to 20 which represents the level of completion each Guild has attained based on the tasks laid before it. Guilds earn boons having completed certain ranks, and these boons like all others in the game add to the IL of a member. example a rank 10 Guild will add 1k IL to a members IL, while a rank 20 Guild will add 2k IL.
b) Campaign completion and the boons associated with said campaign.
c) Gear, this includes armour, weapons, artifacts and companions rank, and the gear they are wearing.
d) Enchantments, these include Weapon and Armor enchantments, runestones (bondings and others) as well as all the enchantments placed in both Utility, Offensive and Defensive on both the character themselves and their companion.
e) Enhancements, these can be made or purchased and can add additional stats and IL to both the character themselves as well as to the companion.
So as you might have noticed, most if not all may actually be purchased, which is why IL offers no measurement of competence or skill. The Alliance views asking for IL in chat a no-no. Requesting the quest (dungeon, que, etc.) implies that an IL or Campaign completion is required also perhaps class type, but beyond that when asking in Alliance chat it is first come first served. As a matter of politeness it is your responsibility to inform the person who is leading the party whether or not this is your first time doing this quest etc. It is up to them at this point to determine if the party make up including yourself has a reasonable chance of completion if this is the goal. If you are finding that you are being excluded more often than not, please inform your Guild leader or Officer and ask them why this might be.