When it comes to the fees, that will be determined by the product(s) you use as the investment vehicles, and I'm in the wrong continent to help there. But, (generalisation coming up) I use my monthly investments to rebalance, so I'm never selling, only flexing what I buy each month, this reduces fees. IE I start out with a 75/25 split, bonds drop during month one , so my portfolio is now 80/20. My next month's purchase goes 100% into bonds to bring it back to 75/25. (Or whatever works to make the numbers work) Of course this only works while your stache is small enough that one month's investment can rebalance it, but it will get you started and you can develop more complex solutions as you get more confident.
Start by ignoring what account everything is in and working out if your ratios are correct overall. Then determine which accounts you are going to be actively adding cash to going forward. I would prioritise tax advantaged accounts that have low charges and low transaction fees. Then simply DCA into your target accounts, but keeping the total portfolio allocation in mind, rather than just that of the account. If you must sell to rebalance, KIV that transaction costs could eat into any potential benefit from rebalancing, I believe once a year is the maximum recommended frequency.