You would have to be constantly earning 8.9e101/minute for 7 days to get to 9e105. Be aware the offline gold gain is different then online gains.

I can't tell you a level you have to get to b/c there is so many factors that go into it. Like what campaign are you running in, how many idols you have, what your formation set-up is like, what gear you have on your crusaders, your trinkets, etc...

The best advice I can give you is to go in whatever campaign you have the highest gold bonus in and go all the way up to your wall. Then push as hard as you can against it. Also save your gold mission to complete once you are at your wall.

Whenever I have a gold daily hanging around for more then a couple days that is exactly what I do it works like a charm.

You're correct, I'm not very good at the game. In spite of buying natilies golden blade and Panda's Golden clover I haven't advanced much in the last year.

The game is almost to complex for a casual player. Trying to figure out what to spend idols in takes a spreadsheet, and the most googled entry to CotLI is "what's the best formation"

After 11 months and 224 resets I have made 4.3e107 gold and 1.7e4 idols. That's it. Not sure why I have TWO missions that each need 20% of the total gold I've ever made and I can't delete them but ok.
Sorry, thanks for the advice but this game annoys me at times.

that you see such a thing is a good illustration of the exponential nature of this game. i.e. when one is at the highest zone that they ever have been to their gold accumulation in the last minute is easily 1-10% of the total of all gold that they have ever accumulated in even thousands of days. check that out the next time you are very high.
but you having two dailies like that is a mystery, if you got one on say some prior run before that reset then it's highly likely that you would satisfy that when you get another similar high one on another run. but circumstances of what those are exactly and where you were when you got those matter i guess.

how to complete them in UNDER 7 days. end the current objective you are on, go do a world wake free play (those are where one can go really far among regular objectives (or this events free play as it also allows really deep runs but not as deep as 2 of the last few events free plays). do not end your run until you are really really far up there and watch those dailies just end nearly instantly when you start getting that much gold per second, not per minute or per hour or per day, but if you get to a high enough area then you get that much gold that quick.

sorry for being long winded, but this is a very good educational topic.