Using a brush with a metal ring on it will cause oxidisation and air purples in your gesso surface, the air bubbles will appear days after you finished gilding. To avoid that you need to use brushes that have no metal on them such as these.
Budget brush for general use
Price range: $2 through $8
Stencil brush, round, pure fair bristle, metal cramp, short handle
Price range: $8 through $18
Gesso Polishing Mottler, Fair Bristles, Natural Wood Handle
Price range: $9 through $22
Flat brush, Black Goat Hair, Natural wood, For General Use
Price range: $10 through $41
Gilder’s Polishing brush, Round Fair Bristle Extra Short Handle
Price range: $14 through $66
Gilder’s Brush for Bole & Gesso Application, String Bound Fitches, Round Oval
Price range: $74 through $197
