Look i think it will be better of to just buy an audio interface !!! Don't buy it brand new, you'll waste your money!!
have a look on the web e you find thousand of them second hand!!

with the interface you can also connect the microphone!!! Which trust me will be very useful in a long run!!!

after you'll need a DAW and i advice ableton!!! cubase , yes you can, but ableton is more professional and good for sampling in the future!!!

If you want a piano!!! i advice an mpk (MIDI Keyboard, which you'll connect to your audio interface) !!!!

i have a few ideas for you, go and have it look !!!!
http://wp.me/P8udj8-1s
http://wp.me/P8udj8-1K
http://wp.me/P8udj8-1Y