Considering the EXP Table here, we know that for a new 5* base unit, you'll need these much LB exp to cap reach certain level at certain cap:

• 5* cap : Lv 1-20 : 36,100 LB EXP
• 6* cap : Lv 20-25 : 17,250 LB EXP
• 7* cap : Lv 25-30 : 112,500 LB EXP

And considering the maximum value of fully fused pot, therefore the best LB EXP value for each pot (optimized for space-saving) are as follows :

• King Burst Pot : 36,100 LB EXP
• Burst Pot : 15,000 LB EXP
• Mini Burst Pot : 2,200 LB EXP

And therefore, when you want to level LB EXP of the new 5* base unit, you will need these amount of those nominals :

• Lv1-20 (36,100) : 1 King (total : 36,100)

  Just the right amount

• Lv20-25 (17,250) : 1 Normal 1 Mini (total : 17,200)

  100 exp deficit, easily solved by adding 1 mini burst pot, which is easier to get

• Lv25-30 (112,500) : 3 King 2 Mini (total : 112,700)

  200 exp overflow. Considering the amount of space saving you do, I think this is a reasonable loss

OK, you're probably wondering why I wrote this. We have just received 100 burst pot in GL and the current state in next couple months will be one of these 3 :

• You already have your unit at 6* maxed their LB, and you got a dupe ready and you want to level the LB from 25 to 30
• You got a new unit in the future, but not enough copy to get 7*, so you'll have to level their LB from 1 to 25
• You got a new unit in the future and you have the second copy, so you want to level LB from 1 to 30.

In no way, that you can level the LB EXP with maxed amount of LB pots nominmal (3.8k, 21k, 40k) without these 2 cases happen :

• Big LB EXP overflow
• Big LB EXP deficit
• Your inventory will be flocked with Burst Pot, because you don't know the optimal LB EXP to reach for each pot so you get the minimum overflow/deficit.

Now, knowing the information I provided, you can save a lot of space without having deficit/overflow of LB of the units you're leveling in the future.

Here's some comparison of overflow/deficit if you go blindly maxed out all the pot EXP

CASE NEW 6* (0~25): 53,350 EXP

With optimal nominal, you will need to feed :

1 King, 1 Normal, 1 Mini.

Total slots : 3

And left with 50 EXP deficit to cap

With capped nominal, you will need to feed :

1 King, then you'll have 13,350 exp deficit. Finally, you'll have :

• 7,650 EXP overflow with 1 maxed burst pot (total slots : 2)

• 1,850 EXP overflow with 4 maxed mini burst pot (total slots : 5)

CASE 6* TO 7* (25~30): 112,500 EXP

With optimal nominal, you will need to feed :

3 King, 2 Mini

Total slots : 5

to reach cap and have 200 EXP overflow

With capped nominal, you will need to feed:

2 King, then you'll have 32,500 exp deficit. Finally, you'll have :

• 9,500 EXP overflow with 2 maxed Burst Pot (total slots : 4)

• 100 EXP deficit with 1 maxed Burst Pot and 3 maxed Mini Burst Pot (total slots : 6)

CASE NEW 7* (1~30): 165,850 EXP

With optimal nominal, you will need to feed :

4 King, 1 Normal, 3 Mini

Total slots : 8

to reach cap and have 150 EXP overflow

With capped nominal, you will need to feed :

4 King, then you'll have 5,850 EXP deficit. Finally, you'll have :

• 15,150 EXP overflow with 1 maxed Burst Pot (Total slots : 5)

• 1,750 EXP overflow with 2 maxed Mini Burst Pot (Total slots : 6)

REVISION:

• Changed the total number for case 6* to 7* on capped nominal due to wrong counting (5 slots -> 6 slots)
• Changed the optimal nominal of Mini Burst Pot from 1,100 EXP to 2,200 EXP, because the gcd of 2 and 6 in previous nominal is 2, so it's better to fuse mini up to 2,200 EXP per pot.