It would be best to station yourself out of Dumaguete. Oslob is a day trip (or maybe stay the night to be able to hit the whale sharks and the waterfalls nearby). There is a ferry going over to Siquijor daily if I remember correctly. You can do day trips there as well but I would recommend finding a resort to stay at for a couple nights to give you more time to explore the island. The resorts there should be able to set you up with tours/transportation. You might want to consider a day trip to Apo Island and the Manjuyod Sand Bar as well.
Apo Island - Getting There and Getting to Know it
Manjuyod White Sand Bar - Negros Oriental
Enjoy Siquijor in Less Than 24 Hours


Thanks x 1