The radio bit will come with practice. You will that a standard procedure is use for most calls - Who you are, where you are what you want. You will them be told how to get what you want. And if they speak too fast, you are ask in plain language "Please speak slower" and they will.
With regard to instruments, learn what you need to know from the syllabus used for your licence. When you are flying hopefully you will be taught that the best "instrument" is the one out of the window (the clocks inside are rubbish and a poor representation of the real world, the one outside your aircraft). Your ears will tell you how hard the engine is working and the noise of the airstream will tell you how fast you are flying. Your hands, feet and bum will tell you if you are doing a good job.
If you have spare time, brush up on mental maths. Your tables are worth learning off pat.
And that's about it.
PM