Here's a few corrections to your post.
1) Summons - Yea just to let you know. I have 3 summons all with full set of runes. I get stats from ALL of them. Removing even 1 rune will reduce my stats. And yes, even on Summons that I am NOT using. Just like Magatama, having 3 level 3 runes is much better than having 1 level 5 since they all stack.

2) Coupons - Please don't use coupons on black market items. ESPECIALLY if you can get them from instance. 5 coupons for a single upgrade material? Are you serious? That's such a waste, just wait the next day or for stamina refresh and you'll probably get it. Anything that you can earn, don't buy it. This includes Battle Armor Cloth Upgrade. The key is patience so your coupons can be better used on other stuff that gives you more power. Example is the Fruit Tree event where you spend the coupons on a Gold Ninja Tool.

3) Extra Tip - Here's an extra tip. Keep levelling. Higher level = More Cultivate and Awaken = More Power. Especially for those that think staying at a single level and farming to the max is a good idea, it's not. You're just stagnating yourself while everyone advances to new heights. To do this best, save all your stamina potions for Monday when you get double exp for sweeping. During that time, aim to upgrade all your equipment or get awakening materials. Don't waste a single stamina on anything else except maybe Rich Field. This means no Strong Approaching on Monday, you have the whole week anyways.

Hope this helps.