Interest

I know that some of my classmates have memorised the periodic table(or at least, part of it). I also know that there is a periodic table song up on youtube that aids people in memorising it because of its catchy tunes and stuff. Obviously we don't need to memorise the periodic table for now, but it would be good to challenge yourself and try, and you will definitely need it in the future.
As for ionic and covalent bonding, some of you who have done the ACE would know that there is an exception to the general rule that metals bond ionic-ally and non-metals bond covalent-ally. Again, this might not be completely useful for now, but there is definitely need for it in the future. (I got my information from a A-level website, so perhaps these exceptions are tested for A-levels.)
However, I think for you to really be knowledgeable in Chemistry (or anything in fact), you will need to be fuelled by the passion. Learning things simply because they are needed for the future won't bring you far. Take a look at the scientists. Most of them do experiments simply because they are curious, and they have passion for experimenting, for knowing, that cannot be doused. Only with interest can you truely excel in anything.