Two things come to mind:
1) General: Based on what you're saying, I have the feeling that you are still in the very beginning of your learning curve. I really would suggest to do some further reading to be a bit better prepared before you spend your hard earned money. Start with
http://jlcollinsnh.com/stock-series/2) Specific: investors domiciled outisde the US, have to pay withholding tax at source to the US. Every time you get dividends or interest paid, you'll end up having your income reduced by the applicable withholding tax. The usual rate is 30%. I.e. If you get 100$ in dividends by owning VTI on dividend pay date, you would only get 70$. This means that non US investors would choose ETF that aren't from the US but domiciled in Ireland. The Irish domiciled Funds (such as all world ETF from Vanguard VWRD) would only get taxed 15%. Hence, usually that's better than going for the US based funds.
But you live in Romania. What's awesome about Romania is that the dividend withholding tax at US source is only 10% rather than 30%. This means you would be better off going for the US based funds like VTI, VXUS etc.
As for bonds, if you decide to add bonds to your portfolio. (Again please do some reading to make an educated decision on your strategy) Should you chose to have US government or corporate bonds, I'd highly suggest to go for an Irish-domiciled bond fund. Why not a US based Fund? Because you'd get your interest payments taxed by the withholding tax (in your case just 10%). But the Irish domiciled bond funds aren't taxed at all. so you get to keep all your interest.
Update: and yes, I agree with Interest Compound. If you go for bonds, go for Eurozone bonds available at global.vanguard.com