I personally highly suggest starting with BTC. BTC is the mother of all other crypto. No matter how good ETH is, at the moment it's still classified as an alt coin.
I agree. Having and starting with Bitcoin either as your main invest or as a contingency is always a good thing. However, it should come with the realization that investments with Bitcoin may take months or even years at a time to be realized because of its trend that it can go dormant or inactive for months before it will surge and catch fire to regain its lost values back. For now, I think the better asset to invest in is Ethereum, I say that because it has more chances to show a gain rather than bitcoin, and in this market, it is so disheartening to take losses after losses, especially if that's you're first venture.
I think you cannot able to buy etherium without bitcoin because there's no such a fiat that can directly could buy etherium coin. It should be buy bitcoin first then trade it in etherium for gas purposes.