Taking the barracks from level 1 to 30 costs 46,400 beast books in total, or 742,400 gems if you buy them (16 gems per book). Here is the full table: what each level costs and how much you have spent by the time you reach it.
| Level | Books | Running total | Gems |
|---|---|---|---|
| 1 | 0 | 0 | 0 |
| 2 | 200 | 200 | 3,200 |
| 3 | 300 | 500 | 4,800 |
| 4 | 400 | 900 | 6,400 |
| 5 | 500 | 1,400 | 8,000 |
| 6 | 600 | 2,000 | 9,600 |
| 7 | 700 | 2,700 | 11,200 |
| 8 | 800 | 3,500 | 12,800 |
| 9 | 900 | 4,400 | 14,400 |
| 10 | 1,000 | 5,400 | 16,000 |
| 11 | 1,100 | 6,500 | 17,600 |
| 12 | 1,200 | 7,700 | 19,200 |
| 13 | 1,300 | 9,000 | 20,800 |
| 14 | 1,400 | 10,400 | 22,400 |
| 15 | 1,500 | 11,900 | 24,000 |
| 16 | 1,600 | 13,500 | 25,600 |
| 17 | 1,700 | 15,200 | 27,200 |
| 18 | 1,800 | 17,000 | 28,800 |
| 19 | 1,900 | 18,900 | 30,400 |
| 20 | 2,000 | 20,900 | 32,000 |
| 21 | 2,100 | 23,000 | 33,600 |
| 22 | 2,200 | 25,200 | 35,200 |
| 23 | 2,300 | 27,500 | 36,800 |
| 24 | 2,400 | 29,900 | 38,400 |
| 25 | 2,500 | 32,400 | 40,000 |
| 26 | 2,600 | 35,000 | 41,600 |
| 27 | 2,700 | 37,700 | 43,200 |
| 28 | 2,800 | 40,500 | 44,800 |
| 29 | 2,900 | 43,400 | 46,400 |
| 30 | 3,000 | 46,400 | 48,000 |
| Level 1 to 30 | 46,400 | 742,400 |