Arabia and arena are gonna be very different.
On arena you can fast castle, castle drop an enemy, and go into conqs.
On Arabia, you CANNOT reliably go fast castle into conqs.
The problem is that it takes forever to build up an army of conqs, and you have to invest a ton into a castle to get them.
Castles are great obviously, but they only defend one place.
If you put it at your base, your ally will get 2v1’d and die.
On Arabia the easiest is to go scouts into knights, but you can also go scouts into a forward castle drop into conqs.
If you put the castle on the enemy base you keep pressure on them and keep them at home so your ally doesn’t just die to a 2v1