As others have said, make your purchases less often. If you are investing for 30 years, there is not much difference between investing $50 this week, or $200 a month from now.

Also, you don't have to literally invest 10/30/30/30 each time. The goal is to keep your OVERALL allocations fairly consistent. If you invest $100 in bonds this month and the OVERALL allocation changes, it just means you don't have to invest in bonds for a couple months.

Also make sure you are not getting charged per purchase. There are two ways to invest in tdeseries at TD Bank (I honestly can't remember the two), but one of them has a cost per purchase. If that's the case, try to change it, or purchase less often.

Good luck with investment journey.