Both Sistani and Khamenei are accessible in English language. Anyone of them will be a good idea
Search that who is most learned scholar and follow him.
Alhumdulillah we are blessed with few maraje , some are in Qum some in Najaf.
Aagha Seestani and Aagha Khamenai are the renowned maraje. According most of our ulama Aagha e Seestani is Aalam and majority of the shia world is doing his Taqleed.