Is there a minimum amount of nodes traffic goes through before reaching it's destination? To my understanding of Tor, every node increases the effectiveness of the encrypted communication.
All Tor circuits contain 3 nodes by default (passing over hidden services which work a little differently and essentially use two circuits chained to a gateway node). Any more than this does not add any extra anonymity.
While it is possible to change the number of nodes by modifying the source code, this is not recommended. Any less than three nodes and your anonymity is more easily compromised, and any more and your latency (and the load on the network) is increased without providing you with any real benefit.
To understand why three nodes is the optimal choice, let's start with one and build our way up. With one node (effectively a proxy) the node knows both who is sending it traffic, and where that traffic is going (no anonymity). With two nodes one node knows who is sending traffic, and what node the traffic will be coming out of (or what the guard node is). This makes it easy to perform traffic correlation. However, with 3 nodes, there is a buffer between these two nodes. Therefore one node knows who you are, one node knows nothing, and the last node knows where the traffic is going but is fully isolated from the input. Adding anymore nodes doesn't do anything else except add more nodes that know nothing between the guard and exit nodes (slowing down everything).