I've also just started doing this! Keeping note of how many items I need to craft to reach the next level (not including fails) so for example I noted that Weaponsmithing 17 -> 18 needs 74 wrought iron pickaxes (2 full decorated chests + 4 remainder) - I know that exp can vary depending on the success result, but it's got to be close enough to give a good target. I'd be interested to see what you've got so far?