You can use a coffee mug as a temporary place for him to hide =) Just be sure when you do get some decor that the holes are more than big enough for him to get through, not too rough, silk plants are better than plastic (if you have to use plastic, run them over nylon to see if they catch - if they do, they're bad for your betta). A 25-Watt adjustable heater will greatly help, and if you havent gotten some already, omega one pellets or new life spectrum and a frozen or live food. As for real plants, some starter ones are java moss, java fern, anacharis, and marimo (moss balls) - low lighting and hardy =) And generally cheap (except the moss balls). Goodluck with your new little buddy! He's beautiful!
Just watch over him till you get everything and you're welcome to come ehre with any questions =D