This is something to work toward, if you find yourself unable to do it now- while sometimes sound effects are needed, as much as possible try to let the art do the talking. Someone who's wheezing has very different body language from someone who is yelping out in pain, vs. someone laughing, crying, et cetera. When dealing with just objects, obviously the idea of "body language" kind of isn't applicable anymore, but motion lines and the way they are shaped can say a lot. A burst of color that sticks out from the page is good at denoting a loud, shocking sound.
However, since you do like using sound effects in your work, like you noted kind of implicitly, there's two ways to go about it- write out the actual word describing the action (wheeze, wheeze, pant, pant) or write out the onomatopoeia. Sometimes one or the other will appear needlessly cheesy in a certain situation. For wheezing, I recommend writing out that word instead of trying to sound it out- I (and I imagine other readers) read that word and have sort of a "stock" sound effect we will automatically hear and associate, whereas certain body sounds are difficult to articulate in our alphabet and may lead readers to the wrong conclusion.
Whether you choose to use the word or the onomatopoeia, the most important technique is to use the visual shape and appearance of the text to convey what you want the sound to be. A word fitted neatly in a word balloon conveys a different effect than text that seems to be barely contained by its bubble. Perhaps, in the case of your gasp, the word is breaking the bubble open, even.
You can also mix what I mentioned about dealing with objects in with your words/sound effects- use motion lines (thoughtfully) with your text! You can also try making the start of the gasp in small letters and the end of the gasp in bigger letters, starting neat and ending rough/"untamed" to convey emotion, starting thin and ending in bold.
Don't kid yourself, friend. I still know how.
"I'd much rather dream about my co-written Meth Beatdown script tonight." -JSConner800000000