I would pick Northern Ring Ranges, overlooking the river towards the east. Overall review this game is a very generous game when it comes to giving you Gold Nucleus, which is quite useful. The game also gives you a lot of Black Nucleus, which is yet another permanent banner with much lower drop rates. However, Dark Crystals can be a lot more difficult to get.
It is impossible to get every weapon in the game as a free-to-play player unless you are absurdly lucky. So you need to save up for weapons that you really want to use. This might a few things I wish I knew before I started play this game. Overall, this game is cool!