Life Situation - I am a 21 year old male and I am currently single and living at home. I have a job working for a family owned lawn-care company. I'm wanting to invest some money because I feel like this is the optimal time because my expenses are very low.
Gross Salary/Wages - I earn $1,800 a month on just salary. Also get a monthly bonus based upon the previous months commission. Generally is about $1,000.
Pre-Tax Deductions - 10% for tithing (yes, I really do base it off gross income)
Other Ordinary Income - during the winter months I help with scorkeeping basketball and they pay me an hourly wage of $8.25, usually only 16 hours a week. Pretty much do it just to help out and isn't a significant source of income.
Qualified Dividends and Long-Term Capital Gains - I have a Roth IRA that I add to with each paycheck.
Current Expenses - I spend around $400 a month which includes my share of the phone bill and gas for my vehicle. It's a gas guzzling truck that gets about 15 mpg, actually looking into getting a new vehicle. Other than that, I don't budget at all. I haven't tracked my expenses to see exactly what I spend my money, which I know is bad and just purely lazy.
Specific Questions - My main question is about investing, I've done some research and my plans are to invest in Index Funds using Vanguard. I would like y'alls opinion on a good amount to invest. Should I invest ASAP, or should I save up some extra cash and wait until January of 2016? I don't know what would be best for me, also any advice/help that y'all would like to offer is always appreciated on some wise financial decisions I should be thinking about in my current situation.