Gokarna and South goa is your ideal destination. However, do note that it is season end and summer is on way, so it will be pretty hot over these places. But if you're just going to chill then these are good destinations. Do check my South goa blog if you want info regarding the same. Else ping me if you want any further help.
As i recently visited Gokarna in the month of January, I would like to suggest Gokarna. This place is budget friendly. It has many secluded beaches. You can go for a beach trek, walk around, and have fun:) Have a great holiday!