If you only have tier 2's then it won't hurt you to start again with the code, it's one of those Nvidia ones and 2500 gold gets you a month premium meaning 50% more credits and XP. I'll pop it over to you via trust.
Honestly i'd either spread myself out and try most up to around T6 so you can get a bit of a feel for how the different nations play, although some dont come into their signatures until even later than that.
Germans - Big targets, usually heavily sloped with good armour and the guns generally are very accurate. The Tiger you mentioned earlier, Tiger (H) is poorly armoured, it's shaped like a box that needs to be angled to bounce anything and even then same tiers will still pen you, prone to fire too. Tiger (P) much better armoured tank but leads to the Maus which isn't a very good tank these days, even my t7&8 mediums will eat it for breakfast unless its back in somewhere i can't get to it's side. The Tiger (H) leads to the E75 and E100 which are much better.
American - Generally medium to low accuracy with ok damage but with awesome gun depression on most of their tanks meaning you can abuse terrain. Their heavies get silly amount of armour on the front of their turrets from T7 up.
French - Low armour apart from their higher tier TDs but fast and some of the lines end up with autoloader tanks, means they have a barrel that holds say 5 or 6 shots that can be fired in quick succession.
Russian - Innacurate guns that do a tonne of damage (122mm is theme for the russian tanks), fast but generally not well armoured until T8+ where you get tanks like the IS3 with a tiny yet very sloped and thickly armoured turret.
Brits - haven't played them and really not sure what they're good at other than the T8 Caernarvon being annoying and their TD's having rapid fire guns and being invulnerable unless you aim for the weak spots.
Chinese - basically the russian tanks with more damage and minuses in other areas like accuracy
Edit - there are some exceptions to what i've written above but its generally how their tanks go, some have a tree that does the opposite where they are better armored and slower than most of the others for example.