Tip#2: Outpost Defense - Upgrade them resource collectors

Upgrade your resource collectors to at least level 3 asap. It makes them look bigger and gives your base an overall more intimidating look. To a potential raider, they appear to be between level 3-5 as well.

Lvl 1 - 2

Lvl 3 - 5

Pics: http://backyard-monsters.wikia.com/wiki/Goo_Factory