Break a word down into spoken syllables. Generally, every syllable in a word contains one vowel sound. Here are some words and their syllables:
bottle: bo (pronounced bah), ttle (pronounced tul)
symmetry: sy (sih), mme (meh), try (tree)
Add the sound "-idiga" after the first consonant(s) and before the vowel sound of each syllable:
bottle: bidiga, tidigle
symmetry: sidiga, midiga, tridigy
Replace the "a" sound in "-idiga" with the rest of the syllable:
bottle: bidigo (bidigah), tidigle
symmetry: sidigy, midige, tridigy
Repeat with every word.
Practice, practice, practice!
Keep in mind that many versions of Gibberish are slightly different. You may need to learn a new "gibberish dialect" if you want to communicate with some folks. A common variation uses "thg", "diggadee", "ithica", "dither" or "ither" instead of "idiga".
In some versions, for words that start with vowels: A becomes "adiga", E becomes "edige", I is "idigi", and U is "udigu"
In Northern England, a popular variation on idiga is iviga, thus making "dog" into "divigog" and so forth.
Another variation is to place the letters "uthug" before each vowel. For example, "hello" would be "huthegelluthego".
Another variation is to place the letters "ib" before each vowel. For example, "hello" would be "hibellibo".
"Egg-Language" is another variation except put the word "egg" into every syllable. Take a hike = T(egg)ake (egg)a H(egg)ike. Just remember to pronounce every broken syllalbe as you would normally say it, and not as I spelled it. Example "head" = is pronounced "h(egg)ed"
Another is "Pig Latin," in which you take the the first letter of the word and put it on the end, then add an "ay" after that. So now "food" would become oodfay. Or "Dog" would be ogday.
Other languages can also be turned to Gibberish. Swahili is a good example because most words don't have compound consonants. The added letters are "~rg~". Asking for a glass of water in normal Swahili is "Nataka maji". In gibberish Swahili it becomes "Natargaka margaji". You can try a similar technique in other languages.
One common version is to add "itherg" after the first letter of each consonant. Example: Bottle becomes bithergottithergul. For a syllable starting with a vowel, replace the "i" in "itherg" with the vowel.changing guy into gigiguy so it would stay the same and for girl it would be gidigirl the same but she would be sidighe