Earn 0.5 BTC a month? I don't think that you can 0.5 BTC in signature if your rank is Sr. Member below maybe Hero member above,
I suggest to you to try trading you can earn beyond 0.5 BTC if your capital is great.
Yeah trading is a good option especially altcoin trading but as you said he need some great capital and i think it will not be a problem because we can get few amount of bitcoin from signature where we can use as capital to start altcoin trading. For me, after halving is the best time to buy altcoins because the price of altcoin will be cheaper than now because they are just relying on bitcoin price.