Because you were giving Tony and I such bad instruction getting to you’re house; we could of gone the wrong way and ended up completely lost and being to late for the party.
1. Verb tense:
The instructions were given at a point in time, so we need to use the simple past tense (rather than the past progressive).
2. Pronoun use:
In the first clause, "you" is the subject of the verb and "Tony and I" is the object, so we need to use the objective case for the pronoun ("me").
We would only use the expression "Tony and I" if it were the subject. For example: "Tony and I got lost".
3. Number error:
"Instruction" is a countable noun, so we need to add an article ("a" or "the") or make the word plural ("instructions"). In this case, we would use the plural since there was likely to be more than one instruction given.
4. Missing word:
We must convey the relationship between "instructions" and "getting to your house", so we need a preposition. Both "on" and "for" are acceptable.
5. Word confusion:
Try not to confuse the contraction of "you are" ("you're") with the possessive pronoun ("your"). In this case, we need the latter.
After a modal verb (like "could"), we need to use use the base form of verb. In this case, the verb is "have". If we contract this verb, it sounds like "of" -- but we must not confuse the two. The phrase should be written "could've".
7. Verb form:
This last clause needs the past participle, rather than the progressive, form of the verb "be" (i.e., "been").
8. Word confusion:
When modifying an adjective, we use the adverb "too" (rather than the preposition "to").
A semicolon is used to join two closely-related independent clauses. But in this sentence, the first clause is dependent, so we should use a comma, not a semicolon.
Because you gave Tony and me such bad instructions for getting to your house, we could have gone the wrong way and ended up completely lost and been too late for the party.