Your pulling on a thread here...
Animation graphs can get complex really fast, but they don't have to be hard to deal with.
You want to have your base state be an "idle". This is what your character does when the player does nothing... no input, no game script acting on it, no physics forces, nothing. It just stands there and breathes, looks around, whatever.
Off of the idle you can look for player input and then blend into "walk", "run", "jump", "crouch", states, depending on your game needs. Walk/Run is usually based in one of two ways... the full range of player input from something like a thumbstick would be mapped to walk/run states based on speed. Anything above/below causes a switch, with an anim blend in between. Another option is a hard button check... "W" means walk, and "Shift" means run. Also, you can often get away with blending from an idle into a walk, but sometimes you will need a specific "start walk" and "stop walk" anim for the transition.
Now here's the complexity... in our W/Shift example... that's two states (nodes). In the W state, you need exit events for "go to idle" and "run", because the player will either stop, or go faster. Going to the idle is done by releasing the W key, and going to run is done with the Shift key is pressed. Be sure to set up the wiring so that run happens even if W is still being held, because that would be the common player behavior.
The shifts between idle/walk/run should start to illustrate where the complexity starts. What if you have jump in your game? Can I jump while walking? If so, the walk state needs and exit to jump. And what happens when you land? Your jump state needs to check what the player is doing, because we could be going go back into a walk, we could have pressed Shift because we want to run, and we might have taken our hands off the controls completely, which would lead to going back to idle. Some of these will blend nicely together, others will need transition animations. (I STRONGLY advise you to try as hard as possible to minimize the amount of animations your character needs!)
I hope that gave you enough to get started. I suggest starting really basic and building up as you need it, rather than trying to build something huge to begin with. The average console game character could have a couple hundred animations! Don't go there! Just start with two or three states, get comfortable working through them, and then you will be ready to start adding more functionality to your character.