I would not dismiss flying entirely. It is not necessarily more expensive than overland travel and you will save a lot of time that you can spend elsewhere.

Travel overland from Istanbul to Georgia and then to Armenia. Travel back from Armenia to Tbilissi. Then fly back to Istanbul. For a departure in one week from now (1st of July 2015) the prices for a one-way ticket start at ~ 70 EUR. Unless you plan to hitchhike, overland travel won't be much cheaper. You can also consider a flight from Trabzon to Istanbul. Flying from Trabzon to Istanbul is even cheaper. For the same date as above, fares start at ~ 25 EUR. 

The option of traveling back via Iran is interesting too. I would then arrange the visa before leaving from home. This way you are sure that you will be able to enter Iran. Or, in the worst case, you know that it will not work for sure. However, there is an additional point to consider. The train from Teheran to Istanbul only runs once a week. This is a kind of a bottleneck and requires good planning. Either, you have to split up the trip into several legs, for which you have more frequent trains, or you have to take a bus. On the other hand, you don't need to go down to Teheran. You can travel from Armenia to Tabriz (Iran) and proceed from there to Van (Turkey). 

There are interesting possibilities. It is a matter of time and planning.

Caucasus: end overland trip where I started without retracing my steps
Suppose I am enumerating reasons not to fly. Is it then correct to write/say:


  Firstly, I prefer the train because I can see the landscape. Secondly, I have control over my luggage, and thirdly, it is better for the environment.


Or is it rather:


  First, I prefer the train because I can see the landscape. Second, I have control over my luggage, and third, it is better for the environment.


I thought the first should be correct, but I find the second one in written texts. Which one is correct?
