Queen Sigma Achievement in Vampire Survivors

The Collection is viewable from the main menu at any time. There are 126 items you need to acquire to complete the Collection. Almost every single achievement is tied to an item in the Collection, so completing all other achievements will very nearly complete the Collection (making this the second-last achievement you'll get in the game), but there are a few that require a little more beyond the achievement, which I discuss below.

Below are three screenshots showing my completed Collection. Under each, I discuss the entries in each screenshot, pointing out any entries that won't come with natural progression or don't have clearly stated unlock conditions.


This first screenshot is almost entirely just standard weapons and their evolutions. Most of this is just everything already shown and discussed in Candybox (5G), which shows all weapons and how to evolve/unify them. Here are the exceptions:
 

• On the sixth row, from the Bone to the egg-looking weapon (La Rumba), those are all starting weapons for secret characters. Each of those characters has an achievement tied to them though (all of the "Reroll" achievements). Completing those five "Reroll" achievements will unavoidably add those five weapons to the Collection.
• The final entry on the sixth row are the Greatest Jubilee fireworks, unlocked with Greatest Jubilee (50G). What's important to point out here is that unlocking that achievement does NOT add the weapon to your Collection. Once you unlock that achievement, you then need to find and use the fireworks in an actual run. If you want, you can start a run with any character, level up, and then you use (hopefully 10 by this point) rerolls to look for the fireworks weapon. If you don't see it, quit and start a new run, and try again. It shouldn't take more than a run or two for it to show up as an option.
• On the seventh row, the fourth entry is the Candybox. This is the biggest pain to add to your Collection. Like with the fireworks, unlocking Candybox (5G) doesn't add it to your Collection. You must find and use it during a run. Unfortunately, unlocking the secret character Trouser, who starts with the Candybox, does NOT work. It doesn't add it to your Collection. You must find it during a run. The Candybox is the rarest item in the game though, so this could take a while. It can only show up in two places: randomly when leveling up (extremely rare), or from a 5-reward chest after you've already maxed all your weapons and items (so, the point where chests would be giving you just money bags). The latter is a guaranteed Candybox spawn, from what I've read at least, but will require playing a run long enough to max everything and then hope for a 5-reward chest to appear. There is unfortunately no way to speed this up, so definitely grab the Candybox as soon as you see it in any run once you've unlocked it.

• In this second screenshot, the first row and most of the second row are just the standard items you'll get in runs.
• The last three items of the second row and the first two items of the third row are only unlockable once you unlock I - Gemini (5G). Once you have that Arcana card, you need to use it in a row and also get the weapons listed. This is easiest done by playing as Pugnala, start with the Gemini card, and then get Peachonne, Ebony Wings, and Gatti Amari in a row, and you'll unlock all of those items in the collection.
• Also in the third row, the gold ring, silver ring, and two red arrows are only available once you get the Yellow Sign relic. You'll be getting all four in order to complete Candybox (5G) 
• All of the green-back items are standard map drops you'll get unavoidably as you progress
• The pink-backed items are all of the relics. Each has an achievement for it aside from the Mindbender (the glasses and nose), but this one unlocks once you get 50 entries in the Collection

The end of the Collection is just all of the Arcana cards. They each have an achievement tied to them (all of the achievements that start with a roman numeral) and can't be obtained until you collect the Randomazzo relic. They all require getting to level 50 with various characters, which is summarized in XXI - Blood Astronomia (5G).