Hi! You have to legalize the business, sis. Register your biz name with DTI, get a business permit from your city hall, and register with BIR. Most potential clients ask if the biz is legal prior to paying and some would ask for official receipts, especially now when we hear reports of travel scams. It's not enough to say you are, you have to have proof you're operating legally.
As for ticketing, note that you need to have your own system (or GDS as know in the travel industry) or you can also be sky agents/partners of airlines like Cebu Pac and Air Asia Zest. There's a bond, of course, but you need to have the permits for this. Then you can get access to rates or features not accessible to the public in the airlines' website. Kasi, sis, madami naman naka subscribe sa e-newsletters and alerts ng airlines so they know when there's a promo na.