Simple facts :

• You don't need 500x grade 10 cards in your binder
  
• It's how many 10's you ever got back from grading that matters
  
• Graded cards can be sent to be graded again and if they come back as 10's, they DO count for the achievement

You can already see where I'm going with this.

An ungraded card has a 38.4% chance to return as a grade 10.

Graded cards sent to grading again have :

• 30% their grade improves by 1
  
• 41% to keep the same grade
  
• 29% their grade decreases by 1

Consequently, a grade 10 card has 71% of coming back as a 10 that will count towards the achievement. That is much better than the 38.4% of ungraded cards.

So if you want to get the Grading Master achievement fast, you can send ungraded cards for grading to get some grade 10 cards. Then you keep sending back to grading any grade 10 you have, you complete all shipments with ungraded cards to get more 10's for the next round of shipping. Rinse and repeat.

You are better off not regrading cards that are not 10's. Even a grade 9 has only 30% to return as a 10, it's better to instead send ungraded cards that have a 38.4% chance to return as a 10.

What I personally did, I graded high value cards, 2 day service. Anything that did not return with a grade 10, I immediately put for sale. Most of the 10's I did send to grading again, except a few very valuable ones that I ended up selling. Selling a 30k card pays for the next 2 shipments, and the value difference between 10 and 9 is huge. I did it that way in part because my shop was already level 102 when the new graded cards achievement got implemented. I had a good bankroll and it obviously helped.

But, If you DON'T have money for the 2 day service, that's fine too. Use whichever service you can afford, the odds of 10's are the same, it'll take longer but you'll save a lot of money. And for someone starting from scratch, pretty sure the big bottleneck is the level 100 shop achievement anyway. That is yours to find out.

I was not even 100% focusing on the Grading Master achievement in terms of what I sent to grading, I even used the 4 day service a few times. And from 100x grade 10 cards to 500x grade 10 cards, it took me only 43 in game days. For the record, getting 400x grade 10 cards from ungraded cards by using the 2 day service would take around 65 days, with average luck.

steamproxy.net/sharedfiles/filedetails/?id=3592046038
A few facts :

• You need 10 cards. 1x grade 1, 1x grade 2 [...] 1x grade 10
  
• It has to be 10 times the exact same card, same edition, same card set
  
• You need to hold to those graded cards, don't sell them before getting the achievement
  
• You need them in your binder for the achievement to unlock
  
• The achievement unlocks when you open a box coming back from grading IF you have your 10 cards in your binder (I suppose it would also trigger if the box you open completes the set of 10 cards, assuming you already had most in your binder)

So the safest way is to pick a low value card that you have possibly 100's of copies of. Sort your collection by "amount", pick a cheap card you have tons of. You start sending copies of that specific card to grading.

The bottleneck won't be grade 8, 9 or 10. The bottleneck will be grade 4, 3, 2 and 1. Why? Less than 1 in 300 card returns to you with grade 2. Same for grade 1. While the grades 8, 9 and 10 will make close to 75% of what you get from grading.

You should naturally get all grades from 10 down to 5, just by grading enough cards. Then it gets interesting. You could wait for a very long time before finally getting all grades that way.

So what you can and should do is pile the low grades you get. Anything grade 5 or less is good. When you have a good amount of those cards, you put 1 copy of each grade you have in a display or something to avoid mistakenly grading those cards again. Then you send the excess low grade cards you have to get graded again. Each of those cards has :

• 30% its grade increases by 1
  
• 41% its grade remains the same
  
• 29% its grade decreases by 1

That means, if you send 8x grade 5 cards to get graded again, you'll get 2-3x grade 4 back, on average. And by repeating the process, you'll work your way to having all the 10 possible grades.

Don't forget to pull aside 1 copy of the new grades you get.

I think it works fine if you set your cutoff at grade 5 or 6. Anything above that, don't bother regrading. Personally I did set it to grade 5, but I'm not claiming it's optimal. Rather than regrading 6's, I opted to send fresh ungraded cards when I needed more cards in the system. It worked fine, even if I was not lucky. I never pulled a natural grade 1, 2 or 3 while I was going for the achievement. Basically, horrible luck, still got the achievement pretty fast. I'm wishing you better luck!

Bonus note.
If after grading a bunch of ungraded cards you start with all grades from 10 to 6, then say 12x grade 5, 2x grade 4 and 1x grade 2, what should you do?

Keep 1x grade 5, set it aside for the achievement. Then regrade all the other 5's, the 4's and also the 2. Why?

The goal is to get a grade 1. If you were to set aside the grade 2, then you'll have to wait until you create new grade 2 cards before you start trying for a grade 1. You end up regrading grade 2 cards anyway. Might as well start trying with the initial grade 2 card you had. It might intuitively sound risky, but it is not. It might actually save you a lot of time.

Good luck!
Have fun!

If you still have a question about those 2 achievements after reading my guide, feel free to post a comment and ask. I'll answer if I'm able to answer.

If my guide helped you, feel free to give it a thumbs up with a simple click. It always feels good to know my guide actually helped someone.

May your card shop prosper! Have fun!