To be honest with you, a jacuzzi tub and high end upgrades (frameless shower) really see their returns and their value when they are in a master bathroom
Aside from that:
A good starting point relates to whether you are going to keep the layout the same.
Whirlpool/Jacuzzi tubs can be ourchase 'free-standing' (a finished front), or built into a base area.
Consider the choices you would like for fixtures thru out the bath. Colors that will work well togther. Tile? if so, what kind and where.
You can save money by doing some of the work yourselves.
Frameless showers are not cheap, but look great. Consider updating your lighting choices, these can make a HUGE difference in the look of any room...
Hopefully this work will reflect on your resale value.
(FWIW - Again, I would not go overboard on the amenities in a home's main bathroom... as opposed to doing 'high-end' upgrades to a master bath....)