Tikku,
while your plan of going with the 50/1.8 first and then switching to a longer zoom is quite good, let me still give you some more advice
If you buy the 50mm 1.8, keep in mind that it is a prime and you won't be able to zoom. Especially for beginners, this can be frustrating. Pros use prime lenses to get the last bit of sharpness and they usually carry a collection of primes of different focal length.
As a beginner, sharpness should not be your primary concern - ease of use should be. You now own the best APSC DSLR currently the market (according to DPReview), the learning curve will be quite steep. By the way, you should maybe stick to AF lenses, especially for sports manual focus can be overwhelming when you still struggle with the rest.
Next pitfall is the fastness of your 50mm 1.8. As a beginner, you will be tempted to shoot wide open - however, the faster the lens is, the more complicated it becomes to get a sharp picture for both you and your camera
This can be the cause for a lot of frustration.
So, if you buy the 50mm, keep in mind that you will need a lot of practise and inside knowledge of your camera to get sharp pictures. Best beginner's advice is to switch to the center AF point (or center 9) and never use f1.8, better to go to something like f2.8ish.
My advice for you would be the Tamron AF 28-75mm 2,8 XR. It's fast enough and it gives you a little bit more reach. I also think it's more forgiving to a beginner since it's a bit slower and (in my opinion) has more reliable AF than the 50mm.
If you're lucky, you can get one for around 200 pounds
You can sell the kit lens on ebay after you got a good copy of the tamron.
You may want to wait with the fast primes until after you have some experience and really need that extra sharpness and speed for your creativity, but that's just my 2 cents.
Yes, and the thing that sucks most about photography as a hobby is that the biggest money sink are not the cameras, but the lenses. Better get used to that
Anyways, wish you all the best for your future hobby, you have a great camera, there's no such thing as a "bad" lens and whatever decision you take, it can't be a wrong one