Depends what you want to see with them. Scenery can take a wide range of binocular choices, but marine wildlife needs wide angle and land animals need high power. I always take my 10x50's and sometimes add my 16x50's
Advice, the more you pay, the better the binocs get! Top, and I mean top brands include Swarovski, Zeiss and Leica. You can get some pocket models of these manufacturers for $500 or so. Worth it. Will last a life time.
Next line includes Wind River, Nikon (Stay away from the zooms), Steiner, and some Busnells and Pentax. Cost $200 - $300. My fav. of these are the Wind River by Lupold.
We went with Leupold Mesa Wind Rivers 10x50 and got them from Ebay for about $65.00 less than the sporting good stores charge. Very happy with them. The optics are crystal clear. Also got a harness which works great. Relieves neck strain, and no flopping against the chest.
You won't need to spend big $ imho. You can get decent Bushnell, etc at Target for less than 50 bucks which should serve your purposes perfectly.
10 power (10x) is the most power you will need. Over that and you'd need a tripod to avoid the shaking. 35mm lens' will do and are much lighter but 50mm will make the image brighter and thus sharper and they shouldn't be that heavy.