For flex i use magic resist atm, this makes me start game with AP-item (Amp tomb)+ 1pot (or no pots if sup)
Faerie Charm*2 (verry OP, allow to stack manaflow superfast, and big base regen, and allow perma-push with w)
for support role you have the option to skip Faerie charm since frostfang-mana regen, and get the cdr-shoes
Ryla-swiftniss (now you have a verry stronk mobility lead, to build another item, before you continue to stack mobility)
Liandry (a bit random, but it makes 1rocket or a tint-q-shot do massive damage since Ryla-slow, and also gives life, and sustained damage),
is discusting combined with arcane-comet (witch also gets cdr from q-hits, thats Big) verry rewarding when spam w in air, with a chance to hit a champ.
Forbidden idol+kindle gem, to spam that 36cdr
Big life belt >> Deadmans >> warmog (you need to save 1100gold extra since you lack itemspace to have armour-item)
Pressence of mind, its big, huge
Since mana-items not do the job for Heimer-tank
They can not chase you down or assinate burst Heimer. No dives, No hooks, No skillshot can hit Heimerdonk
Heimerdonk free to push and poke, blow turret and sent people fountain or punish the ones that stay.
1Turret already will shoot down any enemy cannonfodderchamp if they ignore it.
Max w first, sent them home, spread shot it like ashe-w (but then it acualy benefit from AP-instead of AD)
Safty-turrets, e-q-w, and its punished, skills never miss anywhy since enemy permaslowed.