Crafting Char Lev Vs Item Lev

I have been doing a lot of crafting io was looking for some input on item lev vs char lev and how to make the best craft.....here what i ahve read so far on other sites...the item lev+clvl x .4 gives you a rought craft lev. but now does the lev of the jewel matter to the craft or whats on the items.. in some cases i have seen or what i thought to a direct link to the object properties like resistance and mf or ias but does anyone have any imput on this are there any master crafters out there