The Best Booster Pack deals I found...

TL;DR version: Following kravan's suggestion below, if you go here and sort by "Set Price", you get a fair estimate of the most valuable Booster Packs for your gems.

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I have no life...

So I averaged the value of the cards (using the best BUY order currently available, so I could sell stuff immediately) and divided by the necessary number of gems per booster pack (I only looked through my Game Inventory). Here is the list I produced, expressed in Brazilian cents per GEM BAG.

(Of course YMMV, depending on time and how long you wait to sell your stuff)

1. 100% Orange Juice (112)
2. Deponia: The Complete Journey averages (110)
3. Dark Fall: The Lost Souls (110)
4. 99 Spirits (105)
5. The Dark Eye : Chains of Satinav (101) (Nothing else in my inventory beats the 100 mark, not even those which are NOT listed below)
6. Edna & Harvey: The Breakout (98)
7. Half-Life 2 (95)
8. To The Moon (92)
9. Faerie Solitaire (91)
10. Cinders (90)
11. Titan Attacks (89)
12. The Path (84)
13. Loren The Amazon Princess (84)
14. Super Panda Adventures (80)
15. The Walking Dead (80)
16. Ultratron (80)
17. Day of Defeat: Source (79)
18. 3 Stars of Destiny (77)
19. Bastion 77
20. Deponia 77
21. Edna & Harvey: Harvey's New Eyes 77
22. The Witcher 2: Assassins of Kings Enhanced Edition 75
23. Fortix 2 75
24. Droid Assault 74
25. Endless Legend 71
26. Brutal Legend 70
27. Borderlands 2 70
28. Batman: Arkham Asylum GOTY Edition 70
29. Fortix 70
30. Batman: Arkham Origins 69
31. Offspring Fling! 69
32. Nation Red 69
33. Portal 2 69
34. Oknytt 68
35. Finding Teddy 67
36. Mini Motor Racing EVO 66
37. Red Faction: Guerrilla Steam Edition 66
38. Batman: Arkham City GOTY 66
39. Deadlight 66
40. Lili: Child of Geos 65
41. Pixel Piracy 65
42. SteamWorld Dig 65
43. Defender's Quest: Valley of the Forgotten 65
44. Anomaly 2 65
45. A Valley Without Wind 64
46. Penny Arcade's On the Rain-Slick Precipice of Darkness 4 63
47. Dust: An Elysian Tail 63
48. The Cat Lady 62
49. Alan Wake 62
50. Bad Hotel 61
51. Splatter - Blood Red Edition 61
52. Organ Trail: Director's Cut 61
53. Chompy Chomp Chomp 61
54. McPixel 60
55. Beatbuddy: Tale of the Guardians 60
56. Awesomenauts 59
57. Borealis 59
58. Eador. Masters of the Broken World 59
59. BIT.TRIP Presents... Runner2: Future Legend of Rhythm Alien 58
60. Cthulhu Saves the World 58
61. Psychonauts 58
62. Antichamber 58
63. Dota 2 58
64. Costume Quest 57
65. Cortex Command 56
66. Defense Grid: The Awakening 55
67. BIT.TRIP RUNNER 55
68. Demonicon 54
69. Anodyne 54
70. Beat Hazard 53
71. Gotham City Impostors: Free To Play 53
72. Tropico 4 53
73. Closure 52
74. Defy Gravity 52
75. Dead Island 51
76. Eets Munchies 51
77. Anomaly Warzone Earth 51
78. Afterfall InSanity Extended Edition 51
79. Risen 50
80. PixelJunk Monsters Ultimate 50
81. Rising Storm/Red Orchestra 2 Multiplayer 50
82. A Virus Named TOM 49
83. Gratuitous Space Battles 49
84. Frozen Synapse 49
85. Ballpoint Universe: Infinite 48
86. Satazius 48
87. Dungeons of Dredmor 48
88. Dino D-Day 46
89. Blackwell Deception 45