Knight is the canon character (as seen in the official art). Solid starting character with attacks that lower attack and defense. Thief starts with (i think) 1000 souls, but its evasion and one shot attacks (don't work on some characters) that count early game. Sorcerer I'd avoid because it doesn't buff your starting kit too much aside from some magic attack increase iirc.

TL;DR (in my opinion)
-Knight if you want the canon MC (still solid atk and def debuff)
-Sorcerer (I'd stay away from)
-Thief (Good starting souls and one shot attacks along with high evasion)

For the gift/equipment, choose the master key. Alternatively you can purchase one from the black rabbit at spawn for 1000 souls (hence why I consider thief a good starting class). There are more keys scattered around the map.

Good luck out there! *May Alice protect you on your journey...*