Everyone of the runners who are in the race are here but we can't get started with the first ones until you line up on a starting line.
1. Word form:
In this case, we need to use two words: "every one" -- or use "all" instead.
2. Redundant information:
The word "runners" refers to people who are in a race, so we don't need to repeat that information.
3. Subject-verb agreement:
If we use "every one", which is singular, the verb must be singular, too. That means we need to change "are" to "is". If we use "all" (instead of "every one"), we can keep the plural verb.
4. Pronoun reference:
Who or what does "ones" refer to? Presumably, it refers to the "race", so to avoid confusion, we should say that.
5. Pronoun reference:
Who does "you" refer to? The context of the sentence points to the runners. We can keep the pronoun, but the runners are "they" (not "you").
6. Article use:
There is only one starting line in a race, so we should use the definite article ("the") instead of the indefinite "a".
When a coordinating conjunction such as "but" separates two independent clauses, we need to insert a comma before the conjunction.
All the runners are here, but we can’t get started with the first race until they line up on the starting line.