A weapon cannot broken if you try to make it +3.
And theres no Guide, there is only luck, a not extrem unlucky Item ( yes there exists Items that dont go +3 with Powders + Premium), and use always Lucky Powders for the right degree.
you wont get it to +3 without elexirs, and you can only use the right Powder.
On each item you have written something like degree 4 or degree 8.
Then you need Lucky Powder 4 or 8.
Use 3 elexyrs and 3 powders and when u make +1 move another place when u make 2+ move another place with +3 do same like +1 +2 and u will see its will work my Enchant score is +5 4 deg bow
When you try to plus your item +3 you will need the following things : Weapon Elixir ( x3) Lucky powder x3 ( YOU need this when you try to + up the item or it will mostly fail , it gives luck) .. Also you can try to add lucky stones on the weapon which gives more luck , but u wont need it if youre plussing wep +3
lol -.- i make my Weapons always +3 without any probleme ... Just No lucky powders and it works for me ... its true but when i try to make +4 with or withour Lucky it foldes but sometimes it works .. but when i try to make +5 its insane lol :P