Who wants which gifts in the Witcher
The best resource for this is the Shopping List over at the Witcher Wikia.
The 'condensed version', totaling up all of the various by chapter lists, provides these aggregate numbers:
40 Beer, 1 Wine, 1 Rose Wine, 5 Sodden Mead, & 3 Temerian Rye
20 of any food item. In addition, you'll need 5 Bread, 1 Dried Nuts, and 2 Sugardolls
1 Daisy, 1 White Roses, 1 Red Roses, 1 Tulips, and 1 of any kind of flowers.
1 Lady's Shawl, 2 Gold Shawls, 2 Red Shawls, and 2 Red Gloves.
1 Amber, 1 Ruby, 2 Diamonds, 2 Sapphires, and 1 of any precious gem.
1 Silver Amber or Silver Ruby ring. Which depends on one of the major choices you'll make in Chapter 3. Additionally, 1 of any kind of ring.
5 Beggartick, 5 Celandine, 5 White Myrtle, 6 Fool's Parsley, and 1 each of Feainnewedd, Honeysuckle, Naezan Salts, and a Wine Stone.
1 Red Meteorite
2 Fisstech
1 Perfume, 1 Swallow, 1 White Honey, 1 White Raffard's Decoction, and 2 White Gull.
And finally, for skinnable items, you'll need
- 3 Alghoul Marrow, 6 Alp Fangs, 3 Archespore Juice, 11 Barghest Skulls, 3 Basilisk Hide, 10 Bloedzuiger Blood, 6 Bruxa Blood, 6 Cemtaur Jaws, 5 Cockatrice Feathers, 4 Death Dust, 6 Dog Tallow, 10 Drowned Dead Tongues, 3 Drowner Brains, 11 Devourer Teeth, 3 Echinops Roots, 3 Fleder Fangs, 2 Garkain Saliva, 15 Ghoul Blood, 4 Giant Centipede Armor, 5 Gravier Bones, 11 Kikimore Claws, 9, Shadow Dust or Shimmering Dust, 11 Wolf Pelts, 3 Wyvern Eggs, 10 Wyvern Steaks
If it's not listed above, or you've already made use of one, and you don't have a use for it yourself, you can safely sell it. Consult the Shopping List link above for a more detailed chapter by chapter breakdown of which items are useful where and when.
As you said Trish's potion, Tulips, White Gull, Wild flowers and food(bread).
Chapter II
Prostitutes - in the Temple Quarter will accept any flowers.
Gossip - in the Temple Quarter during the day near the Hospital or the detective's house. Give her Gold Woman's Gloves, Red Woman's Gloves, or a Diamond. You'll probably have to talk to her several times before you have the opportunity to give her a gift.
Declan Leuvaarden on the Dike give him 3 Salamander Brooch to prove your loyalty and receive 600 orens.
Chapter III
Couresan - She's outside the New Narakort Inn. Pay her with orens or a gem (an Amber will do)
Blue-eyed Lass - She can be found in the House of the Queen of the Night. Give her 500 orens (300 if you show her the House of the Night Signet Ring) or a Sapphire.
Townclerk - on the second floor of Town Hall in the Trade Quarter will fool around with you if you call her a naughty girl and give her a Diamond.
Noblewoman dressed all in white in the Trade Quarter near the Town Hall will sleep with you if you give her a Silk Scarf.
Noblewoman near Triss' House in the Trade Quarter will sleep with you for a Kikimore Claw.
Celina - Give her any ring and she'll sleep with you
Peasant Women - You'll find her in the Inn or wandering around the Village. Give her a Sugardoll and she'll sleep with you.
Elf Woman inside the Elven Cave by the Lakeside will sleep with you if you give her food after completing the Daily Bread quest.
This are just some of the things you can use mostly to get some "affection".The list is not 100% complete so unfortunately it doesn't give you good insight on what gifts to sell immediately.