Going from Gunlukbasi to Otogar - shop on left 250 yds from lights almost opposite an A101.
You want ic cephe for interior and dis cephe for exterior.
Best brand filli boya - they do top grade mixed with silicone or trade grade PLUS with Orange logo - mixed with plastic - but 30% cheaper.
For magnolia look at fildisi (means elephants tooth)
Expect to pay 180 lira total for your 15 ltrs best grade or 120 lira for your PLUS grade.
Both can / should be watered down by 10% and if covering same colour and using a roller you can water down up to 25% but mix it in gradually and stir very well.
There are other shops with the filli boya logo around and should be same price. If you want a cheaper b & q type alternative go to Tekzen back towards Gunlukbasi near to Eren Spots second shop and you will pay much less for a trade paint.