What should I do with these items and how to build them?

Merc treads
Rylais
Gunblade
LichBane
Voidstaff or mejais
Rabadons or hourglass

Not in this specific order and if theres any other items I should suggest getting please tell me.

start boots 3 pots get gunblade then rylais and then build some sort of defensive item voidstaff if they're building magic resist and then lichbane afterwards

personally I build her like this. If you have you're rune pages then start with boots plus 3 pots or if not start with dorans or a long sword or amp tome from there get a
Sheen
Rylai's
upgrade boots
needlessly large rod
finish Lich Bane
finish Rabadons
insert a hextech revolver wherever if you're doing poorly
If they start building defense or are natuarly tanky I get a Void Staff after boots and finish Lich Bane soon after.

What I do is start with either boots+hp pots or a doran's blade, then get the other of the two. Then it's sheen>revolver/soulstealer>Merc treads/ninja tabi/sorc shoes>rylais>Rabadons/zhonyas>Lich bane
Then sell your doran's and build a Gunblade, after that, if you lose stacks on your soulstealer or if you chose to get revolver build a WotA.

Conveniently, this build meant that I wasn't hurt by the gunblade nerfs as much as other builds