I am new to DLP. How far in advance do you need to make reservations? Are there any restaurants that need to be booked well in advance or is it safe as a single to just do walk-up seating?
You can make reservations up to 60 days in advance.
For most restaurants you're perfectly safe doing walk-up dining, the only exception I'd imagine would be Auberge de Cendrillon, which is very popular, and as such very busy at all times.
Last time I went there (also by myself), I made a reservation close to the 60 day mark and the only spot open on the day I wanted was at 15:00, everything else was full. And that was late September, one of the most quiet periods in the park.