Gold DLC - I'd say it's worth your price especially if you're endgame. Gotta get all of the eternal seals, man. You can also buy a bunch of weapons and forge.
Museum Melee - Depends if you want weapons - You can get Nohrian/Hoshidan weapons so it's pretty nice. You'll probably have to grind for the weapon you want, but YOU CAN GET RARE WEAPONS. *Cough Cough* Levin Sword *Cough Cough* Shining Bow.
Vanguard Dawn - Worth it - you can get all of the skills on any unit because the bosses have skill books.
Witch Trial - If you want warping units. You CAN get warp on every unit. (Including males.) Just kill every other enemy except the boss. Spawn camp the witches that spawn until a witch (spawns in a pair) appears with the warp book. (I usually find it on turn 11.)
Boo Camp - I don't think it's worth it. I hardly even use it. You can use it to get xp, but I don't find it entertaining enough.
Hidden Truths 1 and 2 - I only really got it for the Grandmaster seal. If you really want the Robin class, or set up a team able to use dragon veins, it's pretty nice. However, you get a preset team, so it can get stressful.
Royal Royale - It's worth it if you want more Dread Scrolls and Ebon Wings. It gets easier as you play it more, once again it's a preset team. It's actually fun in my opinion because STRATEREGEE. [I basically use Team Ryoma and Team Xander because I find it easier.]
Anna on the Run - I don't find it worth it - 2$ for a unit you can only recruit on the first time is meh. I mean, if you REALLY want an outlaw, go for it. Or you just love Anna.
Free DLC - DO IT [Before Awakening] GREAT LORD AND LODESTAR WOOO. [A Gift From Anna 1 and 2] Free stuff~