It is better to get a normal icici credit card first as based on that one can get amazonpay cc for sure after 5-6 months but the reverse is not true & many ppl who got amazonpay cc first had to wait/still waiting for years to get their first normal icici cc, Also, amazonpay cc is excluded from almost all icici card offers on other websites & even on amazon itself the 10% icici card offer becomes 5% instant discount+5% usual cashback (if amazon prime member) for amazonpay card. Also, amazon has a limit on how much amazonpay GV one can buy on amazon using any cc so don't buy much else amazon will limit your acc & all cards used there to purchase any more amazonpay GV on amazon from any account.
If possible, try to get sbi cashback card as your first card as it gives 5% cb up to 5k every month on all ecomm websites but just like amazonpay card it is also excluded from all sbi card offers except for some rare ones sponsored purely by merchant with no relation to sbi card (aka no 10% offer for sbi cb card in any major sale on amazon/fk etc especially the biggest ones in sep/oct bbd/gis sale).