If you are starting from 0 points you get token for free so choose discoverer. If not wait 100% DM event (which is in like 2hours xD), buy DM, buy discoverer token if you are anything below 1 bil points if you will play actively. Send expos, gg 
Maybe consider buying expedition slots but i also recommend if you are not in a hurry to wait for cashback event or discounts, you legit save like 500k DM on commanders + all slots.
Oh right, don't choose kalesh as your race 
Human/mecha can empower your LF techs with their buildings
Humans have eco buildings + can empower LF techs, you can't really miss with choosing them
Mecha have only deut mine but can empower LF techs higher for cheaper price, i don't do this but maybe someone else has planets on slot 15 and full mecha build but idk how good that is.
Rocks is full eco and gives highest buffs for economy buildings, and before someone tells you human metropolis negates that income, no it does not and it never will.
Kalesh is useless
edit: well slot 8 is still best for planet size and metal buff so...you can just google stuff or ask old friends from game 
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1) You're an explorer, gazing at the magnificent ships and resources arriving from your expeditions. Your mouth waters as you think about the next hour.
2) It's been over a week now, you've reached millions of points and you have a lot of colonies, you've set your sights high.
3) You've defeated a few bad actors in the galaxy with your fleet, and now you're acting like a real man.
4) One day, you wake up to find that a colony has joined your system. Realizing things are about to get really heated, you begin to defend yourself and position yourself with your fleet.
5) The player who joined your system is a general class player. He launches an attack on your planet, and you are unable to counter the opponent.
6) He flattens your planet's defenses with bombers and destroyers, then locks down your fleet with Reapers and battlecruisers. Afterward, the battle report is a clean slate.
7) You think everything about your planet is over. But it doesn't take long for you to realize that's not the case.
She sends out pathfinders and takes away the spoils of your planet at top speed, as if scraping the bottom.
9) Now you're relieved because there's no reason for you to want to continue playing.
10) Happy Ending