It depends :
1.How many concurrent user transactions at a time ?
2.Which type of queries ?
5.Other installed and running software(s) on the computer/laptop ?
6.Which type of database i.e. DSS, OLTP, Warehouse ?
7.How many databases ?
8.Can you use EXADATA ?
9.How many and which type of Oracle database feature do you want to you use i.e. RAC, Data Guard etc. ?
10.Network, Security related software and their interaction with database.
On what basis should i select the hardware for the oracle database?
What are the parameters to be analyzed?
one could worse than to start with the installation guide