You should check The main page
And read the rules. and as for levels i would recommend Reading Level ! , Most of @SkyCityXD3 's levels , @Egglord1 's levels and I would also recommend reading The entity list for entities
I would recommend checking out The groups for lore
(Be aware that some groups such as E.S.I.S.P.S have their own hubs)
I would recommend Reading tales for even more lore from other canons
I would also Recommend reading the Canons list also .
Also check the Objects list aswell
IT is very recommended To read all those for a full start.