Well that is the general idea,everybody is trying to do this.There are 2 reasons to why:
Position - Due the random placement,first city can be in a bad position depending on distance to allies/enemies.
Crops - If you want an army with catapults that can actually conquer something you will need the crop with nice oasis.
The problem is,if you are not best farmer in your proximity at the start of the game,by the time you get to 3 settlers closest crops(if there are any at all) will probably be taken.
So you will be forced to take crop that is further away from your capital which can furthermore slow down your progress(based on distance).Crops 9 and especially 15 have bad resource income so you will have to send merchants on longer trips just to start growing your 2nd city.
Another problem is that you will have to separate your army,if you don't want your crop to be someone's farm.Which will increase you army loss in offense and defense.
So basically if you are newer player your best options are:
To focus your capital and make new cities nearby regarding the resources/allies,which means play safe and defensive...and hopefully to take over someone's crop.
To rush for settlers and settle a crop somewhere far away from everybody and ignore your main city and everybody else.You will fall down in rankings a lot but you won't be bothered too much,givin you all the time to build up your army and destroy few cities.