UPDATE 4: Unfortunately Puzzle Pack No.8 just got updated to 100 puzzles, so if you didn't complete it when it had 10 puzzles then you will need to complete all 100 puzzles in one of the packs, bringing the original solution back into play. You can study the packs to see which one you think is statically the easiest for you by viewing what difficultly puzzles are in each pack below.
Another thing to note is if you fail the puzzle just make sure you click continue, you can have one reshuffle per puzzle. You can access this by clicking the down arrow bottom left.
Thought I would mention it again as it can easily be missed or forgotten.
UPDATE 3: Puzzle Pack No.8 only has 10 puzzles and it is confirmed that you can get the achievement from it. I will leave the rest of the guide as it is just in case more puzzles are added but it doesn't seem like it as the final puzzle pack spells "THANK YOU:)!". It is recommended you get the achievement now just in case.
UPDATE 2: Puzzle Pack No.5 did have 54 puzzles but now has been updated to 100 unfortunately.
UPDATE: Puzzle Pack No.5 was released with only 54 puzzles so has a lot less than the other packs with 100 puzzles each, so bare that in mind when reading the guide as the guide was written when only 3 packs were avaliable. Thank you.
Here is a breakdown of the puzzle packs difficulties:
Puzzle Pack No.1
21 Easy
36 Medium
34 Hard
9 Expert
Puzzle Pack No.2
23 Easy
43 Medium
30 Hard
4 Expert
*Puzzle Pack No.3
40 Easy
41 Medium
13 Hard
6 Expert
*Puzzle Pack No.4
32 Easy
48 Medium
18 Hard
2 Expert
*Puzzle Pack No.5
27 Easy
51 Medium
21 Hard
1 Expert
*Puzzle Pack No.6
23 Easy
44 Medium
28 Hard
5 Expert
*Puzzle Pack No.7
23 Easy
49 Medium
26 Hard
2 Expert
*Puzzle Pack No.8 - Info coming soon
- Easy
- Medium
- Hard
- Expert
*Added at a later date.
Original solution:
So based on the diffculties the easiest one to do is clearly Puzzle Pack No.3, it has it a lot more of the Easy/Medium puzzles and the least Hard/Expert puzzles.
Obviously difficulty is what the game developers have rated the levels so that doesn't mean you will find them easy yourself, also doesn't mean Puzzle Pack No.3 is the quickest, it may have more matches per puzzle than the other packs which means it could take you longer, but generally it will probably mean that it's the quickest and easiest.
There is an achievement that relates to Puzzle Pack No.1 which requires you do 4 puzzles in number order so take that into consideration if you've not started the game yet. If you're like me and your most of the way through Puzzle Pack No.1, which naturally a lot of you may have just picked the first one to start on, it's your choice whether you decide to switch to another puzzle pack or just stick to the one you got, or if you plan on just enjoying the game and want to do them all that's up to you too!
You can use hints, reshuffle or restart the puzzles as many times as you like and it will still count towards the total and the achievement.
As of writing this guide there are only 3 puzzle packs. They may deicde to add more in the future, so take that also into consideration when reviewing the guide or thinking about working towards the achievements that easier packs may be added, if that happens feel free to post in the comments and let others know!
So you've got the stats, the choice is yours, hope this helps!