Avanti giro 1 upgrades
 

Ive just bought an Avanti Giro 1 on sale at my local store as a way of getting into road cycling and am interested in what upgrades I should look to make? I could just look at wheels, crankset, cassette etc and upgrade to the giro 4 spec, or could I do it a better way? I have previously played professional team sport but retired and now want to cycle to keep fit but know I will become competitive at this too, just my nature.
Any advice gratefully received?