So your roof is largely NNW facing?
I am assuming that your approach would be to design with the final solution in mind, that way you can build it up and not have unnecessary expenses. I am also assuming that your final "dream" solution would be to minimise Eskom entirely. I am going make an educated guess, from your stated utilisation figures I would say that your utilisation is just under 1000 units per month, around 33 units per day?
This means that your final solution would probably need just over 10 KWp in solar panels. The 8.8K Sunsynk can handle 10.4, so it's cool.
It has two MPPTs, each needs a minimum of 150V to start, but I hear that they prefer it closer to 400V. 500V is max, but to be safe I would try not to exceed 425V. Each MPPT can also take two parallel strings, provided that the current does not exceed 18A. I'd say that its pretty flexible.
Looking at panels, you say you have no problem with space which means that you can play with lower wattage (and perhaps cheaper) panels and just get more of them, although there are diminishing returns with cable lengths and mounting hardware. Also, if you are going to do it in phases, you need to consider panel availability, mixing different types, brands and models over a 3 year period could cause all sorts of problems and inefficiencies. I would opt for a strong brand like JA Solar where I know that I can order a specific panel model 3 years after initial purchase and still be able to get it.
So let's look at the JA Solar 455W JAM72S20, was going for just over 2K last year.
You will need 4 panels to kickstart the MPPT, so your absolute minimum will be 4 in 1 series string, using only 1 MPPT. You can put 9 in series without exceeding operating voltage (425v) at NOCT, but if you really want to be safe (think cold winter's day) it probably needs to be reduced to 8. So max 8 in one series string, but they are still only producing 8.72A, so you can add another 8 in parallel. 16 panels are already 7280KWp, and you still have another free MPPT!
Back to efficiencies, consider wiring both MPPTs for this (if the cable runs are less than 38 metres you can use 6mm cable), and then just add panels as you can afford. 22 panels would give you just over 10KWp.