I planned my wedding in 8 weeks. It really is possible! I've also planned several other weddings.... so
1st of all - decide on budget - doesn't matter if it's $5,000 or $500,000, you must start there.
2nd - consider major expenses and allocate the budget based upon the importance of each area to the bride. (Believe me, there are tons of "formulas" out there, but they can be deceiving depending upon your wants and needs).
Major expenses are:
Attire
Photography
Flowers
Food & reception
Venue
Music
I can probably give you some pointers if you let me know the direction you're going with the wedding. PM me.