Go for Ethereum as this cryptocurrency has high liquidity, usually ranked #2 or #3, right below the BTC, and also suits your budget. You will never have trouble to buy or sell this cryptocurrency. Also, it has a loyal community, thus its value has a high probability of staying stable and rising in the long run.
Volume or good liquidity is the most important if you are day trading, but you cannot expect that the same coin will always be volatile.
The market has billions of trading volume now, if you are trading with less than a million a day, you'll never find it hard to find a high volume coin to trade.