Yea I've notice that some data's are more expensive than others.
Like these:
Aqua data's: 9-12M
Bird data's: 6-8M
Dragon data's: 3,5-5M
Beast data's: 3-4M
Rock data's: less than 1M
(of course there are more types, like insect; plant; devil etc)
But what I want to say is since Aqua data's and Bird data's are more expensive like other.
Why don't you focus on these data's at the Silver Lake.
All you need is a digimon around 45-55 for higher drop rate.
I use an Armor Digivolved digimon which can 1 hit the monster with F2 at lvl 40.
It's a 3/5 digimon that I bought for 400m
And I bought the 100% Armor DigiEgg for 500m (you can also try with the worn DigiEggs for around 100m, but theres a chance that can get failed)
So I only spent 900m for an armor digivolved digimon.
And I farmed at Silverlake for Aquadata's for few hours and this is my result:
200+ Aquadata's which I sold kinda cheap, for 8M = 1,6T
7 glasses which I sold for 85m each = 595M
8 Mercenary eggs I sold for 15m each = 120M
13 Monster cards lvl 2, I used but you can sell it either of course.
That's already more than 2,3T within few hours..
There is probably other ways to earn a lot more money, but this is just my own way to farm gold that I want to share with you guys

The reason why I quit farming is because my inventory went full. So I used the money that I've earned for inventory expansion to be able to farm longer.
My english is not very good..
Please be nice and don't reply stupid things

Press Thank You if this is helpful.
Well my experience is that aqua data and bird data drops slower that's why i better go farm other eggs but i really appreciate your tip and gonna try it