- Increase your max Hearts by +1.
- Inscrease your max Stamia.
- Instantly gain a level.
- Permanently increase your Damage dealt.
Most people find the Stamina upgrade to be the best, followed by Health on the second place. And after this they begin to work on the Damage incease. I would not bother with using any Spirit Orbs on getting extra levels, because you can easily level up by setting up a Lighthouse farm.
How to get Spirit OrbsNow you know that you need Spirit Orbs to get more Health and Stamina, and the next step is to learn how to get the Spirit Orbs themselves. Firstly, you get a lot of Spirit Orbs by doing the puzzles and challenges in the game, including all the Dungeons. You will get 10-20 Spirit Orbs just by playing the game regularly, and it is usually a steady supply of them if you keep explording and doing puzzles.
It's also possible to craft Spirit Orbs, and you need to use the Spirit Crystal structure to craft it. This requires the "Froststrike" skill, deep down in the right bottom corner of the skill tree. With this, use Crystals and Steel to craft the Spirit Crystal, and use this to craft a Spirit Orb.
Each Spirit Orb requires 10x Great Skull + 10x Purple Pigment + 5x Bottled Fairy to craft. The cost will not rise, but these are kind of difficult to get in the first place.
Like other structures, it takes a while to craft the Spirit Orbs from the Spirit Crystal, so have some patience when you want to craft Spirit Orbs to increase your Health and Stamina in Forager.