Everyone will start at level 1. Big note on level 1 is you are not a full blown adventurer you may have taken some quests, done some odd jobs here and there but really level 1 is a person who is just starting out in the adventurer world usually coming from either being a student or just leaving your home.
You can create any character using Player Handbook 1 if you do not want to buy one let me know and I can borrow you mine for creation. If you decide to go with the gold option and buy your starting gear. You can buy anything that your level and gold rolls will allow but no magic imbued items. If you have questions let me know.
Other than that it is pretty well a free decision on what and who you want to be.
If you character is religious you can choose any god you want from the player handbook or make up your own. Maybe your god replaced one of the gods that fell during the great war If you make a deity make sure to give it some story/what it is a deity of, likes/dislikes, etc. The different lands have wildly different beliefs and gods so deity is a free for all.
If you want more info on an area for your character let me know. Some of the areas have sparse info by design. The only areas your character can’t be from would be Voldorma and Bopohka since they are pretty well uninhabited.
If you need a hook to be in Waterdeep for the start of the campaign. It is the big festival of the end of the Great War. It is a massive gathering of people from all over the world with big parades, lots of food and trade, and it is also one of the few times per year when the council announces its proclamations. Other than the festival Waterdeep has many posting boards where people are searching for work or looking for workers.