Here is a full walkthrough with achievements guide for the Gemlands game.
Introduction
An oldschool styled collectathon with plenty of secrets!
Controls:
WASD – Movement
Mouse – Attack
E – Interact
Space – Jump/Double Jump
Q – Triple Jump (When unlocked)
Tab – Menu
Enter – Confirm in Menu
Make sure to Save often
Unlock Portals when you find them
Open all the chests you can for gold
Enemies drop useful supplies
It may be preferred to return to previous areas once you obtain the Sky Feather.
What’s required for 100%?
Collect all Items (Sword, Bow, Feather)
Collect all Gems (500 Main World + 100 Secret World)
Collect all Rainbow Gems
Buy 6 Health upgrades to reach 10 HP (30 Gold each)
Pet the Dog in the Sky Castle
Stand on the Giant Cloud
Defeat the Boss
Everything will be covered, following how I played the game.
Sunny Cliffs
Behind the crates

After you climb up

After the arrow traps

In the house near where you started
(While you are here, walk toward to portal and learn how it works)

Rainbow Gem
Look behind this wall
You can get the last 6 Diamonds after finishing the next area
Emerald Forest










Rainbow Gem


Once all beehives have been destroyed, talk to the Fairy to receive the Bow.

Fire the Bow at this Target

Tower

Take note of the locked gate to your right
Continue forward to the next area
Dry Canyon

Rainbow Gem
Climb up the rock, jump onto the cactus then up again (Make take a few tries)

Jump on the Flying Birds to cross certain areas

Follow the jump pads upward

Fall down

Make sure to take the Iron Key before you leave

Activate both Portals

Tower Part 2

What’s down here?

Now you have the Sky Feather (Double jump then press Q for extra height)
Rainbow Gem:
Go back to Sunny Cliffs and jump up here

Dry Canyon Part 2

Make sure to read the sign

Sky Fleet

Find the Helm Wheel below Deck

Install the Helm Wheel and talk to the Captain

The Ship can travel between the two sides of the Tower once unlocked
Tide Pools

Gloomswamp
Activate the portals at the base of the Gloomswamp then continue onward
A reusable full health heart
Activate the portal before the Sky Castle
Rainbow Gem
Sky Castle

Rainbow Gem
Approach from above

Get onto the Giant Cloud with the jump pads

Pull this lever to activate both lifts

Rainbow Gem
Jump down here

Dimensional Witch
Buy all the HP upgrades you can (30 Gold each)
(Fall, or use the portals to go back to the first area)
Make your way back to Sky Castle

Use the lifts
Heal if you need and finally make your way to the bossIf you want to see how the boss fight goes:
Congratulations!
Don’t forget to save!
Secret Isles

The final task is to collect the remaining 100 Gems
(Some Gems may blend into their environment and others are well hidden, so look closely!
Start off with the Yellow section, which contains 33 Gems.
Then move onto the Pink section (Gems inside and on top of the obstacle)
and finally finish with the Blue section.
Have fun exploring!
Thanks to Na for his great guide, all credit to his effort. you can also read the original guide from Steam Community. enjoy the game.