It takes years of effort to lean bulk. Not months or weeks. In 12 weeks on a lean bulk you can easily add at least a few lbs of lean tissue. But that's it. Absolute max. Don't be fooled into thinking lean bulking is short term. It very much isn't. You will not get huge noticeable gains. If you're strict with your diet, and training, and keep it up for a year, then I reckon a good 6lbs of lean mass is achievable - maybe more. If you don't care about staying to lean, than you can easily put on over 2 stone of mass. However, 2/3rds of that will be fat or water. Then the effort to cut down, and lose a lot of body weight can cripple some people psychologically.
It's your call. IF you're in it long term, take it slow and make it part of your life. If you just want big gains and not worry too much about bodyfat, don't worry too much, if you really don't care and just want to do the old fashion 80s bulk, then absolutely go for it. Just be aware that each have their pros and cons. It's your choice.