Predicting a numeric variable from many numeric variables, how to choose a proper structure?
How much data do you have? this is a regression problem that doesn't require using neural networks, you can solve this by using much simpler algorithms ( SVM, Linear Regression , Tree-based regressors ) ( I'm assuming you don't have millions of rows of data ). As in for the inputs, you can either use the numeric variables x1 to x8 or create some other variables based on those depending on which is more correlated with y. It is the algorithm's mission to go through your data and come up with a function that gives you a y for your X .