There are enough free players who maxed everything without spending a dime. Take for example video chests. Don’t open them, but save them for almost 2 days. With those alone (6-8) you already have plenty of gold. Make sure you have either gold, luck or farm wardrobe, raid opponents that you can beat that give gold or items. Items you can sell.
Then also save chests from ninja event, war season. And most important, don’t be afraid to leave gold unprotected. Say you don’t have kaiser in defense, with max treasure room you can leave 2M gold unprotected. I even don’t mention to boost taverns.
Start with empty treasure room, but full silo and farms. Have video chests in reserve. Raid till farms are empty and silo is still full. Don’t spend any gold, empty taverns and leave gold unprotected and return in three hours. Maybe you lost some gold, but definitely not all, there is a max you can lose. Raid again, empty farms and keep silo full. Empty taverns, still not enough? Activate free gold shield for 3 hours. You don’t lose any gold, since it’s protected. Then come back before gold shield expires. Now raid till either you have enough gold or silo plus farms are empty.
If you still don’t have enough gold, just open video chests. That should give gold to get even 15M gold. I say not for nothing to use gold, farm or luck gear. Gold gear gives extra gold, farm gear gives extra raids(I just use 17-50 bread, depending on gear I use) or luck gear (giving more items in cof. Make sure you raid players that you can beat). With this strategy anyone can get gold for any upgrade. Only thing you need is time. When you can’t invest time, then you should not complain, time is the alternative of spending cash.
I even didn’t mention to sell items, that you also can do to get the missing gold. So fill up inventory slots with sellable items.
Main problem is that many people are afraid to leave gold unprotected for a while. If you leave for example 5-6M unprotected, max 1.5M is stolen, when you leave 7-8M unprotected around 2-2.5M max is stolen. Point is to get a higher starting value of gold, before you raid.
If problem is that opponents you raid that give descent gold are too strong, then first fix that problem.
By using that technique everyone is able to get a completely full treasure room. With it, I kept my workers busy, plus did upgrade troops, spells, research and waves. I didn’t need to spend gems at all.