The beta is divided into three groups, A, B and C, whereof the two first require you to have participated in the crowd sale, unfortunately. But you will still be able to participate in beta group C at an advantage to those who wait for the public launch. Only requirement for group C is for you to hold 10,000 SJCX, which you can start buying now if you want, in order to be ready for beta C launch. You can easily buy in small increments, if you want, e.g. through Poloniex or the decentralized Counterwallet exchange.