Hi Anwesha, if you want a hassle free experience recommend you go for a package. I have attached with this comment few packages, you can click on them to find more details about them. If you want to talk to someone about the packages simply fill in your details in the form and you will receive a call.
If it's budget then cut down number of countries otherwise u will end paying only for travelling one country to the other. Swiss is budget as I need to book hotels/apartments and Swiss pass and u r good to go. apart from that Italy itself will take 7nights to see venice-florence and Rome. even austria needs 6-7nights to see Innsbruck-salzburg and vienna