Firstly you need to understand this:-

To get the rating up, you need 15 cones. i.e from 40 to 41

To get one star, you need 5*15 = 75 cones i.e from 40 to 45

I assign cones only after obtaining 5 cones for a player so I can monitor the progress. I would know roughly that he would need an additional 5 or 10 to the next rating.

Assigning Cones
To assign points, the max difference between two skills should not be more than 20 skill pts. e.g. Attacking 26 Defence 46. You will not be able to assign anymore cones to the defence until you get your attack skill higher than 26. This is explained in the T11 wiki.

The rule I use to assign skill points is I assign more to the core attribute e.g. Striker = Attack, then physical & mental I will keep it at -5 of Attack while defence is -10 of attack

For DMCs, it would be Attack is -5 of Defence, Physical & Mental is -10 of Defence.

That's just me...you can look at your best player and see his current distribution of skill points and you can use that as a benchmark.