How many gigabytes does Windows 7 take?

It is not just a case of how big the Windows 7 installation is.  Your applications will also take up room.  As you refer to an SSD, I assume you will have a separate drive for your data.

My Windows 7 & its applications use up about 35GB of a 69GB partition with my data on another one.  Many people would say that 60GB is the limit and that really it is unwise to go below 100GB.  That is because Windows uses some of the rest of the space while it is working and it needs this room - the only concrete example I know of is that it needs another 25% for use during Defragmenting but if you searched every thread about minimum drive sizes you would find other examples.  My previous installation had used up about 40GB so I just added 50% and called 60GB good enough then added another 10GB for some reason that I never wrote down but was probably equally illogical.  [The sentences in italics were added 2 hours later when I realised I had forgotten to add them before.]

If you search this forum for *SSD* then you'll find plenty of reports by others who have done the same as you & reports of their experiences will probably be of use to you.

 I want to install it onto an SSD without spending too much money. I don't want to spend more than $80.

My guess is that $80 isn't enough. See Try*3's reply and let me add that my C: drive is 188GB