Always keep an eye out for new Artifacts which unlock as you progress through the game, as the newer are always better than their predecessors.

God of Love is the best choice for first-time players as the revenue from the basic structures is boosted and you don't have enough money to upgrade anything else anyhow.

Tap on a bolt on the right side of the screen and then on the purple orb as it will open up an advertisement, and when it ends you'll get five free bolts, after some time you can repeat the process.

As you hit 10 billion you'll be allowed to reincarnate and you should do so as soon as it is made possible to you as it will boost your production significantly. From then on you should reincarnate every several days.