Trade Up Contract : M4A1-S | Knight

100% Trade Up Contract profit. The only downside is that this requires a large investment. Virtually you will require either 10x Desert Eagle | Hand Cannon or CZ75-Auto | Chalice.

Currently, on OPSkins the cheapest out of two items are the Desert Eagle | Hand Cannon.

The reason why it does not matter what type of skin you use for the M4A1-S | Knight trade up is that you can only get Factory New or Minimal Wear condition of the M4A1-S | Knight. It is better to obtain the Minimal Wear condition as it sells slightly higher than a Factory New M4A1-S | Knight. 

To achieve a Minimal Wear M4A1-S | Knight you will need an average float between the values of 0.71 and 1.0. Virtually this can only be achieved with the Desert Eagle | Hand Cannon, as they do come in battle-scarred condition. However if you were to invest into the Desert Eagle | Hand Cannon at $18USD the total would be $180USD, but a resell value of $260USD on the steam market (~$226 USD after tax). 

OPSkins : https://opskins.com/?loc=home

Float : http://csgoprofits.blogspot.com.au/p/float.html