what does getting first seed get? what advantages?

{quoted}

You won't have to play any other number 1 teams in groups.

There are four groups. Number 1 from each of the four regions that made the knockout stage at the midseason invitational will not play each other. On paper, this is an advantage. However, EU is not one of the four regions so their #1 will have to be placed in one of the groups.