This question seems to have several aspects. Let me reinterpret them one-by-one.
So, you speak mainly Russian with occasionally adding several Ukrainian words, and you'd like to know:
- Whether it is grammatical, according to the Ukrainian language rules?
- Would it confuse a Ukrainian-only or a Bilingual speaker?
- Whether it is safe/accepted on streets of Ukraine?
- Whether such mixture makes you a better friend?
Usually, such mixture is neither grammatical according to both Ukrainian and Russian language rules. The only three actual uses are:
- To emphasize the national flavor of an object being discussed, e.g. Russian: пойдем есть пляцки = let's go eat plyatsky (пляцки is one type of national Western-Ukrainian bakery), even if you don't know how to say "let's go eating" in Ukrainian - BTW, it is ходімо їсти;
- The speakers are bilingual and they choose the shortest/most expressive way, regardless what language it is;
- The speaker is not familiar with one of the languages and uses a word from another one in hope the listener would understand;
Would it confuse someone?
Usually not, unless you use some dialectal word which is not used on the mainland Ukraine, e.g. if you've learned it from someone of the Canadian Ukrainian diaspora.
Is it an accepted way of communication on the streets of Ukraine?
This seems to be a subjective part which is hard to answer specifically. To me, since you are a foreigner and a language learner, it is almost obvious you may miss some word and use a substitute from another language.
Makes you a better friend?
Also subjective, but for me, it is definitely, yes. Because of the recent political events, we have a rise of patriotism, and many people (like myself) who used to be Russian-only speakers at home, start to pay more attention to our language (that's why actually this very site could be created, while two Area51 proposals of mine have died silently).
So, unless you meet an anti-Ukrainian nationalist, throwing several Ukrainian words in your speech may make you bond better. Yet again, it is obvious that a foreigner may not know a word in Ukrainian.