Where
Well first of you need a court. These can be quite expensive to build so I just use my local court. I am sure if you do some research into where your nearest local tennis court is you can find loads. Most tennis courts are owned by a tennis club so you may have to pay membership. I pay £5 a year for a key to the tennis court which is very reasonable.
Equipment
Of course you need a tennis racket. Tennis rackets can be expensive and if you are a beginner I recommend a bog standard racket which you can probably buy for around about £20 - £30. This is relatively cheap compared to other tennis rackets which can reach the thick end of £100. I don’t advise beginners buying a racket over £100 as I believe it would be a waste of money. The racket that I use at the moment is the babolat aero prodrive cortex. This is a very good racket which I bought for £150. I would recommend this to experienced players who have a good standard of playing. I would also like to say that my racket suits baseliners who like to put a lot of topspin on the ball.
You also need some tennis balls. With tennis ball you basically get what you pay for. If you buy a pack of four tennis balls for £2 you can expect them to be bad. The makes that I would recommend are Slazenger, Wilson and Dunlop. I use these brands of tennis balls regularly and they have a good quality and good bounce. You can buy a pack of four for around about £8 - £12. I highly recommend ebay as you can find some really good bargains. I bought 100 tennis balls for £50 which is very cheap.
Tennis trainers
Some tennis clubs only allow you to wear tennis trainers on their court. I would recommend tennis trainers to those who play a lot of tennis because with ordinary trainers they wear away easily due to toe drag when playing tennis. New tennis trainers have protection to stop this wearing away from happening. But if you’re a beginner I wouldn’t recommend buying them as they are quite expensive for another pair of shoes and it doesn’t seem worth it for you if you’re only playing occasionally. Tennis trainers normally cost between £35 and £80.
Tennis t-shirts and shorts aren’t a must but I would only recommend to people who play a lot.