How to do Oracle database cluster / Failover without shared storage I have 2 or 3 RHEL 6 servers and I don't want to have a dedicated storage device. I think maybe you can replicate changes from one node of a cluster to another in real-time.

I want to cluster them so if 1 instance fails it can failover to another instance. Maybe even 2 instances running and a load balancer server.

Is there any solution to this kind of cluster?
In this case, you'll be wanting to use a standby database / data guard, rather than RAC (which uses shared storage).

Read Data Guard Concepts and Administration in the Oracle Documentation.

There's a step-by-step installation guide on Oracle Base that walks through setting up a physical standby database here.