Calculating Different Investments altogether? Bitcoin was my first dive into investing. 

I am trying to see how much I made and how well I did. 

I am getting a problem however where I bought multiple times at different periods and prices. 

What's the standard way to calculate how well I did when each order was at different prices and etc? 

So for example: 

if I bought X BTC with Y USD at time t0 
and Z BTC with Y USD at time1 

How would I calculate my return and profits?
The simplest way to calculate would be:

averagecost = ((BTC[t0] x USD[t0]) + (BTC[t1] x USD[t1]) + (so on))/total_BTC

where t0,t1 and so on are different time when you bought.

The above gives you the average cost for all your BTC

Now to know the profit, use the below formula:

profitloss = (current_BTC_price - averagecost) x total_BTC

If profitloss is negative, then you have a loss.

If profitloss is positive, then you have a profit.