The LEGO® Movie 2 - Videogame

This isnt really a full on solution but more of some tips. First, only the bricks count towards the full completion (credit to mathguy for pointing this out). I initially thought you needed to scan every item, but you do not! However, there are some benefits to scanning the items, a large majority go towards the items you need to complete quests. It helps to limit the amount of backtracking you have to do.

Second, dont bother trying to complete all the bricks on your first run through. Almost every world I can think of cannot be completed without having some attachment gained later in the game. Once you beat the game, you will gain the jet pack, which makes all of the collectables much easier to get. The sad thing is no characters have any special abilities. Superman apparently forgot how to fly, the flash can now run in slow motion, and aquaman forgot how to swim. Dont bother trying to use any character besides the base characters, you'll be sadly disappointed.

Third, try to get as many super red relics as you can. These essentially act as the red bricks in this game, however, you cannot buy them and it is completely rng on which ones you get, and what makes it even worse is the fact that you can get duplicates. This makes getting the ones you want even harder to get. The two I found most useful are the top hat and super map. The top hat multiplies all studs and building bricks you pick up by 2, which is quite nice. But the super map is amazing, it essentially acts as a brick detector, cutting down the amount of time your looking at the small mini map in the top corner tremendously. You can equip one hat and one item at a time.

Forth, I ran into the issue of getting all bricks and completing all quests on all worlds, but I was stuck at 455/475 bricks. What I found is that there are 20 buildable quests in the home world (the one with the really long name that served as a tutorial). You get the buildable quests for completing main and side quests in the other worlds. They have a small purple brick by them in the super builder menu in the home world. They essentially add a quest by a character that are pretty much the exact same as those you encountered throughout the game (beat up these bad guys, build this item, be this character, etc).

Lastly, try to break as many crates and grab as many alien invader hearts. They give you a large amount of studs (chests are about 15k, hearts are about 50-60k). These are large boosts in studs so you can buy relics from the shops. Additionally, there is one brick for sale in the shop in every world (except for Goldopolis which is unlocked st 400 bricks, it doesnt have a shop) so if you happen to be at 49/50 bricks, check the shop for the last one. Hopefully these tips helped out a bit!