Well, you can, sort of. You can buy the 90 crown doodad, then sell junk to get your 90 back. But, yeah, no bartering. Cash up front.
What does sign intensity do exactly ? I mean, for Aard and Igni that’s easy to guess (more chance to stun, more damage and burnination respectively) but what about Quen or Yrden ? Quen only lasts one hit regardless, right ?
Speaking of which, you can buy saddlebags to increase your carried weight even further.
Here’s my biggest tip : don’t sell your starting armour. In fact, don’t sell loot tagged “Witcher” in general, period. Crafting regular items only uses base component, but Witcher stuff seems to often require the previous “tier” of witcher stuff as an ingredient.
Don’t skimp on runes for your gear OTOH. There’s a ton of them out there, and you can destroy a socketed rune at a blacksmith if you find a shinier one.
Don’t sell mutagens : there’s a million alchemy recipes to turn a mess of low quality mutagens into a bigger one. Named mutagens can also be used to make special potions called decoctions with varying but usually pretty powerful effects.
Speaking of which : Alchemy is pretty neat this time around : you only ever need to make a thing once. It’ll give you a potion or bomb with N uses. Those uses are all refilled whenever you meditate, provided you have at least one strong alcohol in your inventory which will be consumed in the process. Just the one, for all your alchemical shit. Beer doesn’t work, but alcohest and rye vodka do. Those are plentiful, if you ever run out every tavern has a bunch.
Which means : unlike in Skyrim, or Dragon Age, or Witcher 2 you don’t have to compulsively harvest every last flower out there !
Similarly, oils are only crafted once, they’re forever and you can apply them infinity times, no need to meditate or anything. To balance it out, they don’t seem to last very long. So ABO. Always be oiling.