In Ruthless, Skill Gem drops matter. Support Gem drops matter a whole lot.
Gems cannot be purchased from vendors.
The Fixture of Fate and Death and Rebirth quests each award you a token that can be traded to Siosa for any Skill Gem of level 31 or lower.
Support Gems can only be found as random drops. You cannot obtain them deterministically. Ruthless is a league of item scarcity. When items are scarce, they are exciting to find, exciting to look for and exciting to trade. We are defining Support Gems as items. This means some builds are harder to assemble, and careful planning is needed by SSF Ruthless players.
Gems gain far less experience than they do in regular Path of Exile. It’s a lot harder to level your skills up, which is another axis of reduced character power in Ruthless. A melee character’s damage comes from their weapon. Spellcasters get a lot of their damage from their gems as they level up. This change helps reduce the power gap between these two playstyles that is otherwise exacerbated by item scarcity in Ruthless. It also means that when you’re farming an area for item drops, you can grind for gem experience at the same time.
Almost all movement skills are not available in Ruthless. In this mode, movement skills trivialise game systems that matter a lot more, such as terrain layout, monster body blocking, and actual level traversal.
Here is a full list of movement skills that are not available in Ruthless: Dash, Frostblink, Flame Dash, Lightning Warp, Leap Slam, Shield Charge, Whirling Blades, Blink Arrow, Smoke Mine, Bodyswap and Charged Dash. Venom Gyre relies on Whirling Blades and is hence also not available.
Items that grant movement skills are currently still obtainable, but the skills they grant will have longer cooldowns. We’ll be keeping an eye on this in the lead up to the 3.20 expansion and may modify them if needed.