You can reach 60 days either by extending a 30-day VoA once, or by starting on a Single-Entry Visit Visa C1, which is valid for 60 days from the outset and can then be extended further. Which route is better depends on whether 60 days is your ceiling or just the first stage of a longer stay.
Best if 60 days is your limit: a 30-day VoA extended once. Simple and economical.
Best if you might stay longer: starts at 60 days and extends to 180.
Tell us your plans and we will recommend the route that keeps your options open.
If 60 days is enough, extend a VoA. If you might want up to 180, start on the C1.
Begin 7–14 working days before your visa expires to avoid any overstay.