Once knocked out, keeping it down will be the least of your problems if you taming in the wild. I suggest to build a primitive trap with stone foundations and pillars. Get an argy and pick one up with right click. Drop it off in the trap and keep a distance - it will fight back, and it will hurt. Once down in the trap, it will very unlikely to wake up before it will be tamed. Good luck.
For a low lvl player a lvl 1-45 is good enough to get you going but when you get the kibble a lvl 116-120/150 should be your main goal. High damage means more metal per hit & weight is your 2nd most useful stat to carry more. P.s taming a lvl 145 ankly now ;)