PoE2Source

Wanderlust · Boots
Cheap unique boots with movement speed and freeze immunity. One of the most commonly recommended budget leveling boots — freeze immunity alone is a big early-game quality-of-life win.
Goldrim · Helmet
Unique leather cap with flat resistances to all elements plus increased rarity. Very cheap and a big early survivability boost before your rings/belt start covering resistances.
Lifesprig · Wand
Unique wand with added spell damage and reduced mana cost — a strong, inexpensive starter weapon for any caster leveling through Act 1.
Tabula Rasa · Body Armour
Simple robe with 6 white (unlinked-color) sockets, always fully linked. Removes link/color problems entirely while leveling — pricier than the others, so treat it as a 'buy if you can afford it' rather than a given.

Chromatic Orb
Sell an item with linked sockets that includes at least one Red, one Green, and one Blue socket.
Grants 1 Chromatic Orb. The fastest way to farm these early — any 3+ linked item with off-color sockets works.
Resistance Flask
Sell any flask together with a ring or amulet whose only affix is a resistance modifier (e.g. a Coral Ring with just Fire Resistance).
Returns the same flask, now granting that resistance while it's active. Cheap, renewable resistance cover while your gear catches up.
Orb of Alchemy
Sell a full rare item set: one rare item in every equipment slot, no two sharing the same base type.
Grants 1 Orb of Alchemy. An easy passive source of upgrade currency once you're picking up rares anyway — don't vendor rares individually if you're close to a full set.
Glassblower's Bauble
Sell flasks whose quality adds up to 40% or more (e.g. two 20%-quality flasks, or four 10%-quality flasks).
Grants 1 Glassblower's Bauble. Worth remembering once flasks start dropping with quality on them instead of vendoring them for scraps.

Act 4 — The Dried Lake