Probably put all if u wna maximize the return. The dividend is calculated on the lowest amount in your account for the month. So if you add 2500 for first month, it will only consider that 2500. The following month u add another 2500 and it will consider 2500+2500=5000. But be aware that if you put 2500 on the first/second/third/etc day of the month, i dont think theyll include it cause theyve taken the lowest amount on that month(once the month started, the first day). Someone might need to correct this if im wrong.
If you put all 30k, it will calculate based on 30k till you take it out.

If you can spare the cash, dump it all in. the earlier the better. More returns at the end of the year.