Optimum Nutrition make a really good whey product. But it might not really just be whey that you need. If you want to gain weight, you need to up your calorie intake and put in the hours at the gym. 1st you need to address your diet before looking to supplements, they are exactly that supplements, made to supplement a good diet, not replace it.
If you cant realistically up your calorie intake enough for whatever reason with food alone once you have established a good basic diet maybe try a weight gain formula, im not up to date with which ones are good these days, pro-mass or something like that was pretty well regarded when I used to train with weights but that was 5 years ago. These are high calorie, high protein, meal replacements. If you start to eat regular small meals, say 5-6 meals a day, then instead of all 5-6 being food, have 4-5 based on food, 1-2 based on a shake or something.
Else you can make your own meal replacement or pre-gym(pre-ride) shakes. Doing this is good because you can buy only a whey product and use pure whey after training for quick shot of protein, or use it as in ingredient for meal replacement shakes - meaning you only need to buy one product not two.
I used to do this:
Porrige Oats (just the dry oats)
Milk
Scoop of Whey protein
some melted peanut butter (1 tablespoon warmed up a bit so it becomes runnier)
A chopped banana
Toss in the blender and blend it.
When you look as the products, look for ratio between, whey, soya and cassian protein, low quality products will be dominant in either of the latter. You may as well drink a milk and oat mix and save money if there is a low whey content.
Id advise you to buy these sort of products online, H&B etc sell over prices under specced product i.e. for the price you pay for their whey protein you can buy a better quality one which has a better blend per serving, and provides double the amount of servings.
I dont use supplements these days, hence not up to date on specific products. Personally, I find nothing to beat a bowl of porrige 2 hours and then a banana 30 mins before a ride or the gym and then a pint of milk for helping me to recover afterwards. Apprently there is research that says milk beats recovery products, but I've not seen it, I dont need to see it, because milk works for me.