Gathering time of rss depends on lvl of troops or lvl of barrack?

The amount of troops that you have (which is also increased by the level of the barracks) will affect the amount of rss you can gather. But it does not affect the speed.

The speed of gathering can be improved through various research items and also by using a Gather Bonus item (24 hours) which you can buy from the alliance store.

Research includes items under the City Development research tract and Zone Commemoration