Remember that you won't lock yourself out of guilt, you'll just have to invest more money and materials to get it. You'll always require multiples of a medal to get dots and guilt. There are efficient ways of guilting medals, but those are much more suited towards either mass gacha pulls (like pulling 3 or 4 10x pulls in a row) or farmable medals. The reason is because you NEED multiple copies of a medal at 3, 4, 5, and 6 stars in order to do the guilting efficiently.
So if you have a 6* Cloud and pull a new 3* Cloud, you aren't really "screwed" in the way some of you are thinking. Instead, it just means you'll need to level and evolve your 3* Cloud all the way to 6* before you'll see the dots (and eventually the guilt). You'll always need 7 copies of a medal to get the guilt unlocked. If you happen to snag multiple copies of the same medal, that's when you want to check the charts to make sure you fuse efficiently (to save money and time).