Horwath
Legend
Red wizards are a prestige class, you could only get into when you got certain level in wizard class(5th in this case).
Maybe the best way is to go with feats to implement some features of that 3E prestige class.
Feat;
Red Wizard initiate,
Prerequirement; wizard level 4+, int 15+, must be a wizard specialized in a school of magic(no bladesingers, warmages, etc...)
gain: +1 con or int,
gain one extra arcane recovery per long rest but spell slots gained from both now must be used on your specialized school of magic.
Pick 2 schools of magic, except your specialized school. Those are your minor schools. You cannot learn new spells for those schools by leveling a wizard class and writting them in spellbook from other sources cost double.
You use only half your proficiency modifier for those schools(DC, attack bonus, etc.)
Once per short rest you can use double your proficiency modifier for a spell from your favored school.
at lvl 11 you can use it twice.
at lvl 17, 3 times.
Maybe the best way is to go with feats to implement some features of that 3E prestige class.
Feat;
Red Wizard initiate,
Prerequirement; wizard level 4+, int 15+, must be a wizard specialized in a school of magic(no bladesingers, warmages, etc...)
gain: +1 con or int,
gain one extra arcane recovery per long rest but spell slots gained from both now must be used on your specialized school of magic.
Pick 2 schools of magic, except your specialized school. Those are your minor schools. You cannot learn new spells for those schools by leveling a wizard class and writting them in spellbook from other sources cost double.
You use only half your proficiency modifier for those schools(DC, attack bonus, etc.)
Once per short rest you can use double your proficiency modifier for a spell from your favored school.
at lvl 11 you can use it twice.
at lvl 17, 3 times.