Ready through the Wiki, it will answer many questions. Depending on where you live (USA/EU) drives can go for $11-17 per TB on sale. Then you should also think about parity aka a RAID5, RAID6 in case a drive breaks down. There are plenty of guides when you Google this.

Plus you'd need to buy the hardware CPU, memory, case but this all depends on your use case. Archival storage vs video editing. Homeserver with lots of virtualization or simple data storage. You get the gist.

You will not get a good answer here with a general question like this. Do you research, find your use case, ask detailed answers.