Talon is a really strong champ in my opinion. He can counter any AP-carry mid because of his E spell (gap closer + silence), his constantly harras with W and because most AP-carrys have magic resist in runes. That leaves them with 12-20 armor and you will have about 30 armor pen. That makes every spell and autoattack dealing true damage. of course will their armor increase but you will be buying brutalizer so you will still tear them apart.

Magic resist blues + masteries will leave you with about 47 magic resist wich is really grant against any source of magic damage.
Mana regen yellows make it possibly for you to farm from a distance when it's to dangerous to walk up to the minion and will also make it possibly for you to constantly harras your enemy.
Armor pen quints and armor pen reds makes you deal true damage in the beggining because the enemy AP-carry will buy magic reist and not armor.

You want to start with boots + 3 hp pots because that's provides you with great sustain and ability to escape and chase. After that you will buy 2 doran's blades to give you a little bit more sustain and damage. Brutalizer is a MUST, it gives you armor pen and cooldown reduction wich means more W´s. Mercery Treads for magic resist and tenecity against heavy cc.
After that buy a BloodThirster and start to stack that up. Buy a Phage so you can slow your enemy and trigg your passive. Finish the Trinity Force for more damage and a little attack speed. When you have these items you will be the main target in team fights if you don't have an overfed AD-carry. Therefore you need a Guardian Angel. Finish the Youmuu's Ghostblade and you will have all the damage you need. Since you have around 150 armor and 130 magic resist but not that much hp you need a Warmog's armor.

You do want to max your W for harass and easy farming. Grab a point in E but then spec Q to level 12. The silence on E isn't going up so it's not worth more points until level 12 in my opnion. Grab ultimate when you can and max Q after W cause of the extra damage it provides your burst.

Ignite: It gives you that extra burst and can prevent the enemy AD-carry to heal up or life steal up his hp in team fights.
Flash: It gives you great sustain and chase ability.