It's too difficult to make blanket statements, since it depends on many factors. The first rows are usually reserved for elites (who may even get blocked seats next to them) and everything will change depending on the route, aircraft, etc. I just don't think there is any strategy to maximise the chances of getting a good random seat without status. More than that, the people who have experience flying IB also naturally have status and hence get free seat selection, so it's difficult to get good statistics on this. You can take a look at the very detailed thread on the so-called Theoretical Seating in the BAEC forum (IB's system is not quite the same, but it shows how complicated things are).

Similarly, I don't think you have very good chances of getting an empty seat next to you without status if you pay for seat selection. Flights are usually pretty full and when they aren't they may block seats just for elites. Hence, there are usually more empty seats near the front, but these may not be possible to buy in advance.

So, in your shoes I would only pay for an emergency exit or bulkhead seat if available and otherwise probably check in early and hope for the best.