- Early Game
Spam Shockwave to harras and get runecontrol. Don´t be to aggressive at beginning. When you reach level 6 you can kill most Heroes at mid. Also you should look for good ganking spots.
Make sure you get Manaboots as soon as possible to get enough Mana for your Spells.
- Mid Game
You should have finished your Battlefury about the ~15 - 20 minute mark. Now you should stick with your team. Use the Skewer / Reverse Polarity Combo to initiate teamfights.
If u feel like you can`t get in correct Position you should buy Blink Dagger next. Otherwise build Daedalus next.
- Late Game
Normaly you should be the dominant Hero at this point of the game. Your next Items depend on the Heroes you play against. If you need Lifesteal you have to decide between Mask of Madness and when u have a ton of gold Helm of the Dominator to grade it later up to Satanic. If you need to become more Tanky you should buy Heart of Tarrasque next. Linken´s Sphere is only usefull when your opponents have a couple of strong single target spells or a lot of disable like Scythe of Wise. I think to Black King Bar i have nothing to explain, most should know when it´s usefull ;-)
Forgive my bad english if someone would correct some errors feel free to contact me. The Magnus Mid Support Guide follows soon. Also i plan to insert some Replays of the Builds.