From a more relaxed or normal player, Chap 15 required an acceptable amount of goods until you got to the techs (after the 12th) that asked for 150-300K of the second tier Sentient goods. This would likely reduce your inventory to near zero or even completely. Then "Shrooms" and More Shrooms, Oh and Soap and Bismuth, and then to really make your head spin 2 of each and remember you can only build 1 effectively. So if you are boosted in soap that you will need to trade for 150-300K of Shrooms and Bismuth EACH for some techs and then repeats that for the next set of Techs.
This of course all depends on which server you are on and what Item(s) are hoarded and not available for regular trading. Of course, your FS may be able to help you, but heaven forbid you are the first or second at that level as there will be no way for your FS to support you.
You can use PP to help and take some of the pain away, and Yes MM is really helpful, but as
@Lelanya noted you best have 1000+ to start with.
I had 500+ and used them all and still barely made it thru.
15 is not a challenge, it is Torture, it was designed in a vacuum without regard to the actual gameplay nor the realities of server differences. I ended up with 5 T6 MFG just to get enough goods to trade for the 1,000,000+ sentient goods OF EACH that I needed for the techs. This is not a fun chapter and for some, it will be the endgame, and others will have depleted their city and become broke and quit mid-chapter others say it was no problem and everyone else is overreacting or was just not prepared. We all have our own opinions, yes but HOW does one prepare to have millions of goods that decay every night available for this chapter and do that in the chapter?
Again just my opinion
Edited for a typo and to add something I just thought of ... Chapter 15 is by its design requiring you to step up your game and be on more than 1 or 2 times a day and god forbid if you only play 1 to 3 times a week, you will never get through 15. To me, unless you are spending several hours per day to make and collect T6 goods and Seeds and facilitate trades you will have a very hard time with this chapter.