I personally make 3-4B on Hauntings every hour so it would be pretty easy to go to T4 from there I have 47 lands ATM.
Fastest way to Hansel is 10Guilds 6 in highlands all the rest of lowlands Titans Then build SoS in rest of Highlands one at a time open with L2 Then convert Titans to SoS then Guilds last
For the record: TRUE HANSEL IS 1 TROOP BUILDING. Just throwing that out there. Anyways I converted one by one full upgrades. As a matter of fact I built guilds on my first highlands because it was more cost-effective. After prices hit 40 and above it was cheaper to convert.
The best and most efficient way, is guild Hansel to highland completion then save 1.3tril and do a full conversion.
Converting 1x1 only drops plunder by around 2 mil tops before it goes back up. I went 1x1 and even one level at a time and it really wasn't much of a difference.
I did guilds all lowlands,, then SOS in highlands, when land got expensive and i got impatient i converted one by one, tho my main reason for this was to up my stats so i pay better when i open both ways work, but in my opinion its not wise to have much gold out on a hansel/ spy build.