The single most useful thing you can buy for bird watching is a decent pair of binoculars. The second most useful is patience. Everything else — feeders, field guides, scopes — comes later, if at all.
The numbers that matter
Binocular specs come as two numbers, like 8×42. The first is magnification. The second is the diameter of the front lens in millimetres. Eight times magnification is the sweet spot for birds: enough to see detail at twenty metres, not so much that hand-shake makes the image unusable.
The front lens diameter governs how much light gets in. Forty-two is standard; thirty-two is lighter and good for daytime use; fifty is bright but heavy. For a beginner, 8×42 or 8×32 is the right answer in almost every case.
Weight matters more than you think
You will be holding these to your eyes for long stretches. A pair that is comfortable in the shop may feel like bricks after an hour in the field. Anything over 700 grams gets tiring fast. If possible, hold a pair for a full minute before buying — that is closer to real-world use than the ten-second test you would normally do.
Specs to ignore
Marketing pages will throw around terms like "BAK-4 prisms," "fully multi-coated optics," and "field of view." None of this tells you whether the binoculars are good. Glass quality is hard to spec on paper; the only honest test is to look through them at something detailed in low light. If the image is sharp and the colours look right, they will work for birds.
Price ranges
Under fifty: usable for the garden, dim image, plastic feel. Fine for finding out whether you actually enjoy this hobby. Around one to two hundred: a real step up — sharp, comfortable, weather-resistant. This is the band most beginners should look at. Five hundred plus: noticeably better in low light and at the edges of the image, but the difference is not life-changing for someone learning the regulars.
Buy second-hand if you can. Quality binoculars hold their value and a five-year-old pair from a good brand is often a better buy than a new pair at half the price.