He's my favourite hero, i play 3 out of 5 games with him, so here's a little guide. Note this is my first guide, and english is not my first language. Any criticism is welcome, enjoy reading.

Skill build:
Against heroes with not many nukes Blink, Break, Break, Blink, Break, Void, Break, Blink, Shield, Void,........

Against nukers Blink, Break, Break, Shield, Shield, Void, Break, Break, Blink, Blink, Void, Blink.....

You can skip Spell Shield if you're against 5 agi carries or something like that.

Item build:
Quelling Blade (225), 3x GG Branch (159), Healing Flask (100), Tangoes (90) works best for me, if you're against harassers make poor man's shield first , QB comes after that.

If you think you don't have enough HP, just buy 1-2 bracers, but STR Treads is often enough for me....

After treads i go Yasha->Manta*-> Basher/Vlads depends on who my teammates are, if someone else is buying Vlads, i don't. But it helps farming neutrals....a lot.

*Note: If the enemy team has a lot of aoe skills, i usually don't buy manta just yasha then butterfly.

Core build should be:
QB, PMS, STR Treads, Manta, Vlads, Basher........13-14k gold.....now i can easily kill roshan 1v1 and drop QB for aegis

Items to consider:
Magic stick: good against skill spammers like zeus
Heart of Tarasque: very good if you need the extra HP to survive mass disables.
Butterfly: for even more attack speed and evasion
Buriza: for mega crits
Divine Rapier: if you're sure you won't die...
MKB is fine too, but i don't know how it works with basher, so i usually skip it if i have basher.

Items NOT to buy:
Battlefury: a lot of players will hate me for this, but IMO this item is not made for antimage, I don't like the build up (1200+1400 items) and delays your core items. Sure its good for farming, but manta is enough.
Any ORB effect items: Mana Break is one of the best orb effects, why do u want to throw it away?
Vanguard: Sometimes its good (axe/rhasta/riki/any physical dmg dealer lineup), but usually i don't buy this item, PMS is enough

Early levels:
Your partner should be a ranged hero with some slowing/stunning/hexing skill to keep the enemy near you while you burn away his mana.

If the enemy has a lot of disables , lane with a babysitter (warlock/dazzle are best for this) or just don't pick magina.....stuns can ruin your game.

Try to last hit as many creeps as you can to farm your core fast. You can even try to harass enemies using the Blink and Break tactic*, mostly low HP agi heroes like sniper, drow, void...

Mid levels:
At level 8-11 i continue my farming, or go gank some weak opponents....magina is an awesome ganker if timed correctly......But i usually farm till i have my core...something like this 40% ganking 60% farming.

Late levels:
Every INT hero will fear you now, if you catch them, they will just cry how you burn 192 mana/hit (with manta) and then use void to finish them off......You can also outdamage some good carries if you farmed well.

*Blink and Break: this tactic is used mostly for harassing enemies. Just blink BEHIND them (so if they decide to run they have to walk around you) and start burning their mana.....if you did it well, they will run away and let you freefarm some seconds Against melee heroes its even better, just run to them, start hitting, share hits (most of the time you will win because of Mana Break Bonus dmg and PMS), if you're low on HP, just blink out.

So, that's my short guide, I hope it helped.