Help with structuring my income with 401K and IRA?

[Kin Lay]

Hi everyone,

I graduated from university about 9 months ago and had began working in the corporate world. I earn about $68K per year right now and I am single. My company do 401K with cash balance formula, which it matches $0.75 per dollar on my contributions of up to 8% of pay? 

I heard about the benefits of compound interests and lower taxable income. I don't really exactly know how it works, but I have read some forums and most people suggested the self-direct IRA. I haven't started yet, but I plan to do tax lien and rental real estate investment for sometimes the end of this year.

There are few questions I have and hopefully someone with knowledge can provide me some suggestions:

1) Can I invest both 401K ($18,000) and IRA ($5,500) at the same time?

2) If so, I plan to do 401K and give that money to some adviser to manage it (I heard usually a small fee of 0.5% commission) and do self-directed IRA by myself with tax lien investment (I will change to tax deed investment during recession). Would this be a good idea?

3) How would my contribution limit ($18,000 + 5,500) be different if I were to earn $150,000 per year? How does that impact the taxable income?

4) Is there a better suggestion for me?

Thank you for all your recommendation in advance!

Let me know if you want me to provide more information.