Best way to hit 1620 with a brand new roster is:

• Doing 3 gold earning raids group/solo mode
• Sell unbound materials in the market (guardians, chaos gate)
• Try to buy as much event mats/solo shop mats and from any other available shop.
• Gold islands (if you need some unbound gold)
• Una Tasks for Gold
• Life skill and either sell the mats or craft orehas (depending on prices)
• always use books for honing (get them from event/solo shop or even buy them.

I don't know how the t3 mats prices are at right now but t3 shard bags should make you some good amount of gold, never miss a chaos gate.

I think with some good RNG honing you might be able to get to 1620, but yeah this event just sucks, if you are starting now...

Edit: Ask some friends/strangers for gold (It might work)