Take a look at this post mate for weight gainers...
best mass/weight gainer it's just a question that I came up with a few answers recently along the lines of what you're asking.
Basically though, I've tried several weight gain/meal replacement products and while they mostly do their job, I prefer now to make up my own as I go along.
The ingredients look pretty good in that MP weight gainer. It would be okay to use as a PWO shake too.
I would, however, buy unflavoured impact whey and some ultra fine oats. tbh, it is more of an initial cost, but I think, if you have room for storage it's worth buying the 5kg of each. This would set you back about £45 but... I had this order just before Christmas and only had to reorder some stuff last week. You will, of course, need tubs with these products as they come in bags. The bags will keep the powders dry but I'm not sure they will last long if you go in them every day for a scoop's worth. That might be a little of £50 for the order, so if this is too much, you could go for smaller potions to see if you can get on with it.
And don't forget a shaker if you don't have one. I have both types and would say the one with a whisk inside is best but only because it's easier to clean, they both blend pretty well.
Creatine. It's up to you really. It isn't too expensive. I started training for a few months before I tried it. It isn't necessary though and I'd say for 4 months at least jusst spend the extra tenner or so on extra food.
PS if you do buy just the impact whey with a flavour or w/e, if you have a blender, you can add normal porridge oats if you blend the oats first it's not too bad. Also, weetabix works, it doesn't taste as nice though.