I got 20,140 scores in CThulhu campain. I only used one investigator: Marie Lambeau "Witch Blood". Since the last update, 1.1.5, the game become significant easier. During this play, I didn't get any +3 dooms midnight effect. Usually, I got stamina/sanity decreased or +doom for each deep ones available and only a few time, got +2 doom. Beside, I got a significant number of -1 doom relic adventure rewards. I made few mistakes: 1- trigger +1 doom terror effect, only one time. 2- allow +2 doom midnight effect of an adventure to be triggered, only one time. 3- I finish the game with 3 dooms token have not been taken yet. If I didn't make these mistakes, my scores can be much higher. But the semi-final Euro football game between Portugal and Spain distract me ^^. I must admitted that, Marie Lambeau's ability "Witch Blood" is too powerful. In my opinion, she is the best investigator. My strategies:
1- Read help guide, it is very useful, from main menu, select HELP->HELP GUIDE
2-Focus on adventure with elder signs rewards, until you have nearly enough elder signs. But don't focus too much on these adventures if you don't have "enough" items to ensure a victory. So, it is good to defeat easy adventures first to get enough items, particular common and Unique items, because more glyphs are always better. Save COMMON and UNIQUE items for hard adventures.
2- Solve locked Glyph as soon as possible, solve adventures with harmful midnight effects and kill monsters that generate harmful effect at midnight before midnight.
3- Sometime, you need to recover your stamina and/or sanity, or buy items. It best to do that IN THE TURN BEFORE MIDNIGHT. Because in that turn, if you solve one adventure, maybe another adventure with midnight effect appears and midnight come right away, triggers that bad effect.
4- Save items that can HEAL your stamina/sanity or both, these items are invaluable, particular in adventures that random take away 0-3 sanity/stamina, combine with one more sanity and/or stamina reduce when you finish or fail that adventure, the result can be sudden dead. And save items that allow you to ALTER GLYPH.
5- When you come to the ocean in Cthulhu campaign, try to find all the amulets before enter R'lyeh.
Here, I save some pictures. You can see how many and what items i have before final battle, and the amount of money, and the final scores: