Your question is too vague. Give us some details as to what you're looking to answer.
My question is
If production environment support 100 users but i want 200 users to have access.So do you think i can go for tableau reader for the remaining users ? hope you got my point.
Well, technically, yes you can use Reader. Then it's how would you be getting the updated report to them. If you have to email it, yuck! (well, I guess using an email distribution list wouldn't be so bad), but if you simply can drop the updated report into a network share then they can download a copy of it at their leisure.
IMO it depends on what you are trying to accomplish. Using Tableaue Reader, packaging the workbook and forwarding it on to the users every time you want to do an update to the information seems like a lot of work. Tableau server makes everything accessible at any time with automatic updates. That being said, it isn't free so you would have to weigh the cost benefits of buying or increasing your user licenses.
Working for a private, medium sized company, we determined there was sufficient benefit to making the reports a pull (as opposed to the e-mail push) and avoiding the reader scenario.