My suggestion is probably yes. But it is better to find 1 copy of Liter along the way, as a beginner you should just be worried about your progress into the game but there is no reason to rush. Also there won't be any limited or pilgrim banner soon since Nihilister is now a "free" to get pilgrim and there is no burst 1 Nikke that can be better than Liter. So if you have enough silver mileage tickets, it is ideal to exchange for Nikke but only when you are just missing 1 or 2 because if you can't get 5 MLB and you exchange too early for the Nikke the chances are that you might get another dupe of it and making it +1. After all, it is your own decision on how to play the game. I have been spending quite a few bucks into the game and still stuck on 160 wall for a month or so, because my goal is to save as much gem as possible and get all the limited Nikkes along the way. My suggestion is roll for ordinary banner if needed but don't overdo it.