All officially published material not from a setting-specific sourcebook is allowed. If you aren't sure if a book is specific to a setting or not, ask.
In addition, material from the Sword Coast Adventurer's Guide is allowed, as that is the sourcebook specific to this setting.
For your background, you may choose any two skill proficiencies and any two tool/weapon proficiencies or languages.
Use point buy for stats.
When creating a low-level character, your equipment follows RAW: you start with the equipment provided in your class features and background OR the starting wealth listed for your class, which you can use to purchase equipment.
If you are creating a character at level 5 or higher, you get a different amount of money with which to purchase starting equipment, and a certain number of free magic items. Use the following list instead of your class' starting wealth and equipment:
Level 5-10: 500 + 1d10×25 gp, 1 common
Level 11-16: 5,000 + 1d10×250 gp, 1 common, 2 uncommon
Level 17-20: 20,000 + 1d10×1,000 gp, 1 common, 2 uncommon, 1 rare
You can forgo getting two free magic items of one tier in order to start with one free magic item of a higher rarity tier. For example, you could give up two uncommon items to start with one rare item. This can stack with other free magic items; for example, at level 17 you could start with one common and one very rare magic item.
Spells: If there is one specific spell that fits perfectly for your build, that isn't on your class' spell list, let me know, and I may allow you to take it as a class spell regardless.
I have not yet finalized every single house rule for this setting. However, here is a preview of the most important changes, so that you can more easily decide which setting to start in for the first arc of the campaign. In general, playing in the Forgotten Realms is designed to be a combination of how most people run DnD 5e games plus how DnD 5e was initially designed to be run.
Most common variant rules apply: Variant Human, feats for ASIs, etc.
All Action Options from the DMG are usable in combat (climb, disarm, mark, overrun, shove aside, tumble)
Major EXP is given for uncovering ancient forgotten knowledge.
Feats are given as story or milestone rewards.