Vacation London Or Paris IM Wanting To Vacation To London Paris And Rome. How Far In Advance Should I Start Making Arrangements?

IM wanting to vacation to London Paris and Rome. How far in advance should I start making arrangements? - vacation london or paris

I'm really new ride on the lake and wondered how much time I should start booking flights and Ill do all the activities in the oceans? So I need to buy any type of temporary visa for this trip?