I would buy ADA. Cardano cryptocurrency is not just another coin, but a real technological platform, with the help of which the team of this project promised to solve all the shortcomings of the digital money market and blockchain technologies. So she has great prospects and I think it's a great option for you!
Both of NEO and ADA are worth for investing. But I will choose NEO. I think NEO has potential to surpass ETH in the future and its price is at very low now. So this is the good time to buy it.