what those nodes are getting?
Nodes don't earn anything for validating transactions.
With running your own node and help the network to be more decentralized. The other advantage is that if you run your own node, you wouldn't rely on third parties for checking your balance and transactions history and you can broadcast your transactions by yourself and in this way, you can protect your privacy.
One person X runs a node, and validates the transaction, right? and the second person Y (miner) can create a new block and can add this validated transaction coming from X to this block.
Right, but just to be more accurate:
Miners don't have to receive transactions from nodes. It's possible that a miner include their own transactions to the blockchain or they receive a transaction directly.
If a miner include an invalid transaction, the block will be rejected by nodes.