I am a relative newbie myself, started golfing just a little over a year ago. Below are some tips/advice that you might find helpful in choosing clubs based on my own experience, and below that are my thoughts concerning your specific questions:
1. As a beginner, your swing will undergo many changes over the next year or so. As such, your ball striking will not be consistent, and you will be hitting the ball all over the clubface, not to mention hitting lots of fat shots, digging your irons into the ground. It would be a shame to buy a brand new set of clubs only to put significant wear on them over the course of the next year or so until you establish a repeatable swing. That being said, if money is no object, then by all means go ahead and spend as much as you can afford.
2. Indeed, It is usually never a good idea to spend a significant amount of money on brand new clubs as a beginner when there is a marketplace full of second hand clubs that you can play with and beat up without spending much money. People give up golf all the time and upgrade their equipment constantly, which means you will be able to find a nice set of second hand clubs for a small amount of money. Once you have a repeatable swing, or are consistently scoring in the low to mid 80's, then you can go out and buy a brand new set of clubs and be able to enjoy them and take advantage of the latest technology built into the clubs.
3. The best place to find a nice second hand set of clubs is either craigslist or ebay. Craigslist is nice because you can meet someone and actually take a look at the clubs before you buy them. Ebay may get you a better deal. Stick to the brand names (Taylormade, Callaway, Titleist, Ping, Cobra, etc.) and you should be able to find a used set of irons for around $100-$150. Craigslist usually has people selling their entire set, including driver, woods, and putter, for around the price you are looking to spend on a brand new set of irons.
4. You want to avoid the really low end clubs. I made the mistake of buying a used set of Walter Hagen's off of ebay for $100.00 (whole set, including the bag). I thought it was a great deal until I had them for a few months and realized they were a terrible investment. Again, a used set of brand name clubs should be just fine as a beginner.
5. Another reason to buy second hand: you may start playing golf and give it up within a short period of time. Golf is expensive and frustrating, people give it up all the time. You do not want to find yourself giving up golf 3 months down the road after having spent $1,000 on equipment when you could have spent a couple hundred.
6. Save money on the clubs and invest in some lessons. I recommend buying a series of multiple lessons (4-6), that will do wonders for your game as a beginner. Make sure you find a good pro and just work with them.
In response to your questions:
1. Are these irons suitable for a beginner like me? (I'm 30, 5.7", 32.5" wrist-to-floor, slim build, more like a women hahaha)
The Razr X irons are great clubs, IMHO. They are game improvement irons and have a large head and nice wide sole that makes striking the ball much easier for beginners. I also think they are remarkably well balanced and make swinging the club a piece of cake. These are great clubs for anyone, including a beginner. You can probably find a used set for 1/2 the price as you will be spending on a new set.
2. Is the lack of 5 iron problematic if I get better and go to the course? My brother use the 5 a lot and he said I will need one.
Yes, if you play full courses, you will want a 5i. Although you could simply replace your 5i with hybrids, as you noted below. The best practice for a beginner, however, is to have a set of 4-pw/sw and learn to strike the longer irons solidly, then make the move to hybrids. If you start with hybrids, you will then have trouble when you improve and want to move to a set of more traditional irons.
3. I'm planning to add 4 and 5 hybrid (RAZR X) when I get better, along with 1, 3 and 5 woods (RAZR X Black) so I will have a complete set, I got an old hand-me-down putter already. Are these hybrids and woods suitable for a beginner? And can the 5 hybrid replace the 5 iron most of the time?
All of these clubs are suitable for a beginner. You may want to hold off on the 3 w for a while and only use a driver and 5 w. A 5 w is much easier to hit and, when I first started, I was able to get much more distance off my 5 w than my 3 w. Hybrids are great clubs and I carry one specifically for hitting those long shots out of the rough. As for driver, make sure you get a 10.5 degree driver or more, this is the loft angle of your driver and will ensure you get the ball in the air more consistently. Again, there is no reason to buy these clubs brand new as you will be beating them up as you play for the first year or two. You can find great second hand drivers, fairway woods, and hybrids online.
Hope this helps and good luck!