Don't try to use the old spelling if you are a foreign student.
Partial use of the old orthography will endear you to nooneno one. Neither is it likely that the occasional "daß" will make you look out of date. Many people have continued to use "daß" while not applying most of the other concerned old orthography rules because most people never knew them.
But the simple truth is that for more than 15 years students have learned the new orthography, most texts are printed in new orthography, and it will be practically impossible for you to learn the old orthography properly.
The reform was heatedly debated more than 15 years ago, not now, and I suggest not to listen to people who emphasize their high level of language sensitivity by comparisons of rape and orthography reform, but YMMV.