G'day Pavan,
This is a very subjective question and depends solely on your own circumstances.
In terms of getting your ATPL theory exams done, it all depends on what you want to do in the short term. If your goal is to become an airline pilot right off the bat, then it would be a good idea to knock out these exams as most airlines prefer a frozen ATPL (you require 1500 hours, to hold or have held an MECIR and potentially take a flight test after September to be granted an ATPL) as it removes one of the barriers to granting someone a command position. This is fairly true for high-end GA RPT operators also, however in most cases you require a few thousand hours to be competitive. Personally, my end goal is to be in the airlines, however I don't want to discount the life experience a good high-end GA charter gig would give. Therefore I have decided to wait a little bit before doing my ATPL theory as it wouldn't be relevant to my short-term career aspirations (I won't be flying a B767 anytime soon) and it would increase the material required to be re-learnt when I go for an airline interview.
As for the instructors rating, it again depends on what you're wanting to do with it. Having not completed one myself, but knowing a lot of people who have and based on what they've told me, I can say that it significantly increases your level and understanding of flying. At the end of the day, an IR may get you that allusive first gig.
As for career options after CPL, again this is highly subjective. You'll find that most skydiving operations will hire fresh CPL holders (this is the avenue I took), and will even give the right candidates a go on a turbine right away. You will also find some Charter/Scenic flight operators will hire fresh CPL holders also (see Kakadu Air). However, remember that most operators will require you to have an instrument rating before they will even look at you.
This industry is HIGHLY competitive, and you could be a born natural, with amazing flying ability and a strong understanding of theory but still not find a gig anywhere. It is SO important to get your name out there, go and network (it's as much about WHO you know as WHAT you know). You have an advantage in that you're doing it through a university and your lecturers are most likely highly experienced in their fields. Make friends with them. Learn from their experiences, and see if they know anyone in the industry that may be able to get you that first gig. I have done courses through Swinburne and UNSW and I make the most of each lecturer and have made friends in some fairly high places within the industry.
There really isn't a "step-by-step guide" to becoming an airline pilot. Everyone's route is different. You may want to go through an airline cadetship (although I know airlines like REX and QLink have postponed intakes due to lack of demand) or you may wish to start off in GA. My biggest piece of advice is go and research entry avenues (direct entry or cadetship) and requirements for whichever airline you wish to get in to, and set yourself goals. Remember that you're not going to be given Captain straight away and you are going to have to start at the bottom. Before I got my first gig, I stuck around the operation every weekend, cleaning planes, sweeping floors and helping wherever I could, just waiting for a position.
I hope this answer doesn't seem like a cop-out, I just wanted to stress that any advice anyone gives you MUST be tailored to your goals and your circumstances, as there is no 'one-size-fits-all' approach.
I hope this helps.
Cheers,
Dan