For the uni club you'll have to try out to see if you make on of the teams before you can join (there's 5 teams and then usually a recreation squad too). Then you need AU insurance (think it was about £5-£8 but I can't get the price 'cause I bought it already) and either £60 for 1st-4th teams, £50 for the 5th team or £40 for the rec squad. There will be kit costs, but I don't know how much.
If you're not on a uni squad then you can compete for your hall in IMS. For that you just need an IMS shirt (think they're about £20) and if there's a lot of people wanting to play for your hall you might have to go through try-outs, or swap in instead of playing whole games.
There are also local Loughborough clubs, but netball's not my thing so don't know much about them.