Quick answer
Всегда́ ра́д!
vsegdá rad — plus не за что and обраща́йтесь — the three Russian “you’re welcome”s
The options
Which when
Пожа́луйста works everywhere — the same word as “please”, which surprises learners. Не за что plays down the favour and is the friendliest. Обраща́йтесь is for help you could give again, often in a professional context. На здоро́вье belongs strictly after food or drink.
рад agrees
Рад is a short adjective: a man says всегда́ рад, a woman всегда́ ра́да. The same word appears in рад помо́чь (happy to help) and рад тебя́ ви́деть (nice to see you).
What you hear back
Typical mistakes
На здоро́вье — after being helped with a suitcase
Пожа́луйста. / Не за что.
На здоро́вье is only for food and drink.
Всегда́ рад — said by a woman
Всегда́ ра́да.
The short adjective agrees.
Check yourself
When is На здоро́вье correct?