Hello everyone who is looking at this build. I am not a good writer so i am gonna make everything short. This is how i play with Elise i mostly use her Spider from to hunt for kills.
(I usualy dont make build so i wanted to try out )

I go with Magic Penetration and mostly with Ability power runes and ofc. Vitality just so i can survive longer that most of the APs do.

I go balanced masteries so in human form my W and Q would do nice dmg and then in spider from when using W i will have more Attack Speed so i will kill them faster. And i put a little bit in defence so i can take some dmg.

Well items are simply balanced mostly focused on Ability power and Attack damage and ofc. a little in Attack speed.

For Summoner Spells i pick Ignite and Flash so i can easy get away from enemys and well burn them a little.

So this was my build and as i said i am not a very good writer but if anyone wants to tell me what i should add to make this even better go ahead i will appreciate it.