Do you sometimes wait for line movement to increase your Arb?
Sometimes the line is clearly moving in your favor, so do you put the soft bet in and wait and see if you can do better with the steam? Or is that "gambling?"
If you do, what Books are best to watch for early and leading line movement, so you can see if you should wait for an even better number or grab your number now? Is Pinnacle the first to move?
What you are suggesting isn't arbing and it isn't outright gambling, it is in the middle of the risk spectrum as it is trading.
The line might be moving in your favour but it doesn't mean it won't move against you in the next few minutes and wipe out the arb and even leave you with a loss. If you have a good arb that you can make profit from and you are risking that by seeing if you can eek out further profits by seeing if the line moves further in your favour, in my view that is an unnecessary risk. I'm in this for profits that are as risk free as possible and for me, waiting for the line to move when you already have a good arb is an unnecessary risk.
Each person has a different appetite for risk so before you go any further, you need to decide whether you want to be an as risk free as possible arber or a risk/reward trader, as being somewhere in the middle is likely to muddle your thinking and you probably won't be as successful as you should be or successful at all so you need to have a set approach on whether you take an arb if it's there, or if you take the risk of seeing if the line moves further in your favour whilst having the chance that the line moves against you.