It's a disease to worry about. It comes with fever, cold like symptoms, eye pain, body pain and bone pain (Break bone fever). All the blood counts go down especially platelet count which may give nasal and oral bleed.
So Platelet count is good initial investigation which should cost you less than 100 rupees. but beware, on first and second day, these may be normal and serial counts may be required. If strong suspicious is there, go for NS1antigen testing (Within first week of fever). In second week Dengue serology (IgM & IgG antibodies) can be ordered.
I have come across few cases where platelet counts have dropped to 9000 which have been saved by platelet transfusion, also couple of unfortunate deaths. so indeed early diagnosis is needed.