Pokemon-go – What are all the ways to get stardust

Like Samthere said, you can delay indefinitely, however id recommend keeping one Pokemon high to take gyms with. Don't power it up more than you have to but keep it high enough to get at least a few gyms. The extra star dust and coins you get should be worth the candies and stardust you spend to keep just one Pokemon high. I usually get rid of anything with a CP meter under 90%. It's probably good to set a goal like level 25, otherwise you probably will delay it indefinitely. Lastly, go ahead and evolve any Ratatas and Spearows (or other really common ones in your area) you can for the experience. Their evolved forms max out pretty low so they aren't really viable later, otherwise leveling will get really slow unless you are hatching eggs left and right.

There are several ways to get XP in the game. I've copied this from the Pokemon GO Wiki.

• Win a fight with a pokemon at at an opposing team's gym: 150 XP

• Fighting a pokemon at an opposing team's gym: 100 XP

• Win a fight with a Pokemon at a gym that belongs to your team: 50 XP

• Capturing Pokemon (100 XP)

• Adding new Pokemon to your Pokedex, whether seen, caught, or evolved (500 XP)

• Evolving Pokemon (500 XP)

• Going to Pokestops (50 XP)

• Hatching an egg (500 XP for new Pokemon or 200XP for existing)

• Capturing a Pokemon with a Nice Throw (10 XP bonus) OR

• Capturing a Pokemon with a Great Throw (50 XP bonus) OR
• Capturing a Pokemon with an Excellent Throw (100 XP bonus) OR
• Capturing a Pokemon with an Curve ball (10 XP bonus)

All of these can be doubled by using the Lucky Egg item